Burj Dubai Concept, Design and Construction Presentation
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Transcript of Burj Dubai Concept, Design and Construction Presentation
Burj DubaiConcept Design amp Construction
Introductionbull Burj Khalifa (formally Dubai) is the new
tallest tower in the worldbull Construction began on 21 September
2004 amp completed on 1 October 2009 bull The building was officially opened on 4
January 2010bull Height of the Tower is 828m bull Itrsquos Owner is EMAAR Properties with total
investments of US$ 15 billionbull The tower is designed by Skidmore
Owings and Merrill (SOM) bull Adrian smith was chief architect
Worldrsquos Tallest Buildingbull From the head start it has been
intended that the Burj Dubai be the Worldsrsquo Tallest Building
bull The official arbiter of height is the Council on Tall Buildings and Urban the illinois Institute of Technology in Chicago Illinois
bull The CTBUH measures the height of buildings (measured from sidewalk at the main entrance)
bull Burj Dubai is the tallest skyscraper to top of spire 828 m
bull Building with highest occupied floor in the world163rd floor
Worldrsquos Tallest Buildingbull Highest outdoor observation deck in the
world (124th floor) at 452 m bull Worlds highest elevator installation
situated inside a rod at the very top of the building
bull Worlds fastest elevators at speed of 64 kmh (40 mph) or 18 ms
bull Highest vertical concrete pumping (for a building) 606 m
bull Worlds highest installation of an aluminum and glass facade at a height of 512 m
bull Worlds highest New Year fireworks display
Architectural ConceptThe context of the Burj
Dubai being located in the city of Dubai UAE drove the inspiration for the building form to incorporate cultural and historical particular to the region
The influences of the Middle Eastern domes and pointed arches in traditional buildings spiral imagery in Middle Eastern architecture resulted in the tri-axial shape of the building
Architecture
Burj Dubai includes163 habitable floors plus 46 maintenance levels in the spire and 9 parking levels in the basementFloor Area 309473 m2
The Residences900 residence from floor
Armani ResidencesArmani Residences Dubai
has been designed personally by Giorgio Armani 144 suites
Hotel (L39)
Residence (L108)
Spire
Observa-tory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureThe observatory
On level 123 At the Top Burj Dubai is a must-see attraction and offers breathtaking views of the city and the surrounding emirateConnected to the tower are The Offices a 12-storey annex of prime office space
The Corporate Suites Are located on the highest levels of
the tower They occupy 37 floors with the top three floors merged into a single office Express lifts take office visitors directly to a lounge lobby at Level 123
Hotel (L39)
Residence (L108)
Spire
Observatory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureMechanical Floors
Seven double-storey mechanical floors house the equipment that bring Burj Dubai to life Located every 30 storeys the mechanical floors house the electrical sub-stations water tanks and pumps air-handling units etc that are essential for the operation of the tower and the comfort of its occupantsBroadcast and Communications Floors
The top four floors have been reserved for communications and broadcasting These floors occupy the levels just below the spire
Main Structure amp DesignThe tower superstructure of Burj Dubai is designed
as an all reinforced concrete building with high performance concrete from the foundation level to level 156 and is topped with a structural steel braced frame from level 156 to the pinnacle
Designers purposely shaped the structural concrete Burj Dubai ndash ldquoYrdquo shaped in plan ndash to reduce the wind forces on the tower as well as to keep the structure simple and foster constructability
The structural system can be described as a ldquobuttressedrdquo core Each wing with its own high performance concrete corridor walls and perimeter columns buttresses the others via a six-sided central core or hexagonal hub
Main Structure amp Design
Structural Analysis amp Design
The top section of the Tower consists of a structural steel spire utilizing a diagonally braced lateral system
The structural steel spire was designed for gravity wind seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999) The exterior exposed steel is protected with a flame applied aluminum finish
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Introductionbull Burj Khalifa (formally Dubai) is the new
tallest tower in the worldbull Construction began on 21 September
2004 amp completed on 1 October 2009 bull The building was officially opened on 4
January 2010bull Height of the Tower is 828m bull Itrsquos Owner is EMAAR Properties with total
investments of US$ 15 billionbull The tower is designed by Skidmore
Owings and Merrill (SOM) bull Adrian smith was chief architect
Worldrsquos Tallest Buildingbull From the head start it has been
intended that the Burj Dubai be the Worldsrsquo Tallest Building
bull The official arbiter of height is the Council on Tall Buildings and Urban the illinois Institute of Technology in Chicago Illinois
bull The CTBUH measures the height of buildings (measured from sidewalk at the main entrance)
bull Burj Dubai is the tallest skyscraper to top of spire 828 m
bull Building with highest occupied floor in the world163rd floor
Worldrsquos Tallest Buildingbull Highest outdoor observation deck in the
world (124th floor) at 452 m bull Worlds highest elevator installation
situated inside a rod at the very top of the building
bull Worlds fastest elevators at speed of 64 kmh (40 mph) or 18 ms
bull Highest vertical concrete pumping (for a building) 606 m
bull Worlds highest installation of an aluminum and glass facade at a height of 512 m
bull Worlds highest New Year fireworks display
Architectural ConceptThe context of the Burj
Dubai being located in the city of Dubai UAE drove the inspiration for the building form to incorporate cultural and historical particular to the region
The influences of the Middle Eastern domes and pointed arches in traditional buildings spiral imagery in Middle Eastern architecture resulted in the tri-axial shape of the building
Architecture
Burj Dubai includes163 habitable floors plus 46 maintenance levels in the spire and 9 parking levels in the basementFloor Area 309473 m2
The Residences900 residence from floor
Armani ResidencesArmani Residences Dubai
has been designed personally by Giorgio Armani 144 suites
Hotel (L39)
Residence (L108)
Spire
Observa-tory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureThe observatory
On level 123 At the Top Burj Dubai is a must-see attraction and offers breathtaking views of the city and the surrounding emirateConnected to the tower are The Offices a 12-storey annex of prime office space
The Corporate Suites Are located on the highest levels of
the tower They occupy 37 floors with the top three floors merged into a single office Express lifts take office visitors directly to a lounge lobby at Level 123
Hotel (L39)
Residence (L108)
Spire
Observatory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureMechanical Floors
Seven double-storey mechanical floors house the equipment that bring Burj Dubai to life Located every 30 storeys the mechanical floors house the electrical sub-stations water tanks and pumps air-handling units etc that are essential for the operation of the tower and the comfort of its occupantsBroadcast and Communications Floors
The top four floors have been reserved for communications and broadcasting These floors occupy the levels just below the spire
Main Structure amp DesignThe tower superstructure of Burj Dubai is designed
as an all reinforced concrete building with high performance concrete from the foundation level to level 156 and is topped with a structural steel braced frame from level 156 to the pinnacle
Designers purposely shaped the structural concrete Burj Dubai ndash ldquoYrdquo shaped in plan ndash to reduce the wind forces on the tower as well as to keep the structure simple and foster constructability
The structural system can be described as a ldquobuttressedrdquo core Each wing with its own high performance concrete corridor walls and perimeter columns buttresses the others via a six-sided central core or hexagonal hub
Main Structure amp Design
Structural Analysis amp Design
The top section of the Tower consists of a structural steel spire utilizing a diagonally braced lateral system
The structural steel spire was designed for gravity wind seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999) The exterior exposed steel is protected with a flame applied aluminum finish
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Worldrsquos Tallest Buildingbull From the head start it has been
intended that the Burj Dubai be the Worldsrsquo Tallest Building
bull The official arbiter of height is the Council on Tall Buildings and Urban the illinois Institute of Technology in Chicago Illinois
bull The CTBUH measures the height of buildings (measured from sidewalk at the main entrance)
bull Burj Dubai is the tallest skyscraper to top of spire 828 m
bull Building with highest occupied floor in the world163rd floor
Worldrsquos Tallest Buildingbull Highest outdoor observation deck in the
world (124th floor) at 452 m bull Worlds highest elevator installation
situated inside a rod at the very top of the building
bull Worlds fastest elevators at speed of 64 kmh (40 mph) or 18 ms
bull Highest vertical concrete pumping (for a building) 606 m
bull Worlds highest installation of an aluminum and glass facade at a height of 512 m
bull Worlds highest New Year fireworks display
Architectural ConceptThe context of the Burj
Dubai being located in the city of Dubai UAE drove the inspiration for the building form to incorporate cultural and historical particular to the region
The influences of the Middle Eastern domes and pointed arches in traditional buildings spiral imagery in Middle Eastern architecture resulted in the tri-axial shape of the building
Architecture
Burj Dubai includes163 habitable floors plus 46 maintenance levels in the spire and 9 parking levels in the basementFloor Area 309473 m2
The Residences900 residence from floor
Armani ResidencesArmani Residences Dubai
has been designed personally by Giorgio Armani 144 suites
Hotel (L39)
Residence (L108)
Spire
Observa-tory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureThe observatory
On level 123 At the Top Burj Dubai is a must-see attraction and offers breathtaking views of the city and the surrounding emirateConnected to the tower are The Offices a 12-storey annex of prime office space
The Corporate Suites Are located on the highest levels of
the tower They occupy 37 floors with the top three floors merged into a single office Express lifts take office visitors directly to a lounge lobby at Level 123
Hotel (L39)
Residence (L108)
Spire
Observatory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureMechanical Floors
Seven double-storey mechanical floors house the equipment that bring Burj Dubai to life Located every 30 storeys the mechanical floors house the electrical sub-stations water tanks and pumps air-handling units etc that are essential for the operation of the tower and the comfort of its occupantsBroadcast and Communications Floors
The top four floors have been reserved for communications and broadcasting These floors occupy the levels just below the spire
Main Structure amp DesignThe tower superstructure of Burj Dubai is designed
as an all reinforced concrete building with high performance concrete from the foundation level to level 156 and is topped with a structural steel braced frame from level 156 to the pinnacle
Designers purposely shaped the structural concrete Burj Dubai ndash ldquoYrdquo shaped in plan ndash to reduce the wind forces on the tower as well as to keep the structure simple and foster constructability
The structural system can be described as a ldquobuttressedrdquo core Each wing with its own high performance concrete corridor walls and perimeter columns buttresses the others via a six-sided central core or hexagonal hub
Main Structure amp Design
Structural Analysis amp Design
The top section of the Tower consists of a structural steel spire utilizing a diagonally braced lateral system
The structural steel spire was designed for gravity wind seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999) The exterior exposed steel is protected with a flame applied aluminum finish
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Worldrsquos Tallest Buildingbull Highest outdoor observation deck in the
world (124th floor) at 452 m bull Worlds highest elevator installation
situated inside a rod at the very top of the building
bull Worlds fastest elevators at speed of 64 kmh (40 mph) or 18 ms
bull Highest vertical concrete pumping (for a building) 606 m
bull Worlds highest installation of an aluminum and glass facade at a height of 512 m
bull Worlds highest New Year fireworks display
Architectural ConceptThe context of the Burj
Dubai being located in the city of Dubai UAE drove the inspiration for the building form to incorporate cultural and historical particular to the region
The influences of the Middle Eastern domes and pointed arches in traditional buildings spiral imagery in Middle Eastern architecture resulted in the tri-axial shape of the building
Architecture
Burj Dubai includes163 habitable floors plus 46 maintenance levels in the spire and 9 parking levels in the basementFloor Area 309473 m2
The Residences900 residence from floor
Armani ResidencesArmani Residences Dubai
has been designed personally by Giorgio Armani 144 suites
Hotel (L39)
Residence (L108)
Spire
Observa-tory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureThe observatory
On level 123 At the Top Burj Dubai is a must-see attraction and offers breathtaking views of the city and the surrounding emirateConnected to the tower are The Offices a 12-storey annex of prime office space
The Corporate Suites Are located on the highest levels of
the tower They occupy 37 floors with the top three floors merged into a single office Express lifts take office visitors directly to a lounge lobby at Level 123
Hotel (L39)
Residence (L108)
Spire
Observatory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureMechanical Floors
Seven double-storey mechanical floors house the equipment that bring Burj Dubai to life Located every 30 storeys the mechanical floors house the electrical sub-stations water tanks and pumps air-handling units etc that are essential for the operation of the tower and the comfort of its occupantsBroadcast and Communications Floors
The top four floors have been reserved for communications and broadcasting These floors occupy the levels just below the spire
Main Structure amp DesignThe tower superstructure of Burj Dubai is designed
as an all reinforced concrete building with high performance concrete from the foundation level to level 156 and is topped with a structural steel braced frame from level 156 to the pinnacle
Designers purposely shaped the structural concrete Burj Dubai ndash ldquoYrdquo shaped in plan ndash to reduce the wind forces on the tower as well as to keep the structure simple and foster constructability
The structural system can be described as a ldquobuttressedrdquo core Each wing with its own high performance concrete corridor walls and perimeter columns buttresses the others via a six-sided central core or hexagonal hub
Main Structure amp Design
Structural Analysis amp Design
The top section of the Tower consists of a structural steel spire utilizing a diagonally braced lateral system
The structural steel spire was designed for gravity wind seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999) The exterior exposed steel is protected with a flame applied aluminum finish
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Architectural ConceptThe context of the Burj
Dubai being located in the city of Dubai UAE drove the inspiration for the building form to incorporate cultural and historical particular to the region
The influences of the Middle Eastern domes and pointed arches in traditional buildings spiral imagery in Middle Eastern architecture resulted in the tri-axial shape of the building
Architecture
Burj Dubai includes163 habitable floors plus 46 maintenance levels in the spire and 9 parking levels in the basementFloor Area 309473 m2
The Residences900 residence from floor
Armani ResidencesArmani Residences Dubai
has been designed personally by Giorgio Armani 144 suites
Hotel (L39)
Residence (L108)
Spire
Observa-tory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureThe observatory
On level 123 At the Top Burj Dubai is a must-see attraction and offers breathtaking views of the city and the surrounding emirateConnected to the tower are The Offices a 12-storey annex of prime office space
The Corporate Suites Are located on the highest levels of
the tower They occupy 37 floors with the top three floors merged into a single office Express lifts take office visitors directly to a lounge lobby at Level 123
Hotel (L39)
Residence (L108)
Spire
Observatory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureMechanical Floors
Seven double-storey mechanical floors house the equipment that bring Burj Dubai to life Located every 30 storeys the mechanical floors house the electrical sub-stations water tanks and pumps air-handling units etc that are essential for the operation of the tower and the comfort of its occupantsBroadcast and Communications Floors
The top four floors have been reserved for communications and broadcasting These floors occupy the levels just below the spire
Main Structure amp DesignThe tower superstructure of Burj Dubai is designed
as an all reinforced concrete building with high performance concrete from the foundation level to level 156 and is topped with a structural steel braced frame from level 156 to the pinnacle
Designers purposely shaped the structural concrete Burj Dubai ndash ldquoYrdquo shaped in plan ndash to reduce the wind forces on the tower as well as to keep the structure simple and foster constructability
The structural system can be described as a ldquobuttressedrdquo core Each wing with its own high performance concrete corridor walls and perimeter columns buttresses the others via a six-sided central core or hexagonal hub
Main Structure amp Design
Structural Analysis amp Design
The top section of the Tower consists of a structural steel spire utilizing a diagonally braced lateral system
The structural steel spire was designed for gravity wind seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999) The exterior exposed steel is protected with a flame applied aluminum finish
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Architecture
Burj Dubai includes163 habitable floors plus 46 maintenance levels in the spire and 9 parking levels in the basementFloor Area 309473 m2
The Residences900 residence from floor
Armani ResidencesArmani Residences Dubai
has been designed personally by Giorgio Armani 144 suites
Hotel (L39)
Residence (L108)
Spire
Observa-tory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureThe observatory
On level 123 At the Top Burj Dubai is a must-see attraction and offers breathtaking views of the city and the surrounding emirateConnected to the tower are The Offices a 12-storey annex of prime office space
The Corporate Suites Are located on the highest levels of
the tower They occupy 37 floors with the top three floors merged into a single office Express lifts take office visitors directly to a lounge lobby at Level 123
Hotel (L39)
Residence (L108)
Spire
Observatory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureMechanical Floors
Seven double-storey mechanical floors house the equipment that bring Burj Dubai to life Located every 30 storeys the mechanical floors house the electrical sub-stations water tanks and pumps air-handling units etc that are essential for the operation of the tower and the comfort of its occupantsBroadcast and Communications Floors
The top four floors have been reserved for communications and broadcasting These floors occupy the levels just below the spire
Main Structure amp DesignThe tower superstructure of Burj Dubai is designed
as an all reinforced concrete building with high performance concrete from the foundation level to level 156 and is topped with a structural steel braced frame from level 156 to the pinnacle
Designers purposely shaped the structural concrete Burj Dubai ndash ldquoYrdquo shaped in plan ndash to reduce the wind forces on the tower as well as to keep the structure simple and foster constructability
The structural system can be described as a ldquobuttressedrdquo core Each wing with its own high performance concrete corridor walls and perimeter columns buttresses the others via a six-sided central core or hexagonal hub
Main Structure amp Design
Structural Analysis amp Design
The top section of the Tower consists of a structural steel spire utilizing a diagonally braced lateral system
The structural steel spire was designed for gravity wind seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999) The exterior exposed steel is protected with a flame applied aluminum finish
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
ArchitectureThe observatory
On level 123 At the Top Burj Dubai is a must-see attraction and offers breathtaking views of the city and the surrounding emirateConnected to the tower are The Offices a 12-storey annex of prime office space
The Corporate Suites Are located on the highest levels of
the tower They occupy 37 floors with the top three floors merged into a single office Express lifts take office visitors directly to a lounge lobby at Level 123
Hotel (L39)
Residence (L108)
Spire
Observatory (L123)
Communication (L160)
Office (L153)
Pinnacle
ArchitectureMechanical Floors
Seven double-storey mechanical floors house the equipment that bring Burj Dubai to life Located every 30 storeys the mechanical floors house the electrical sub-stations water tanks and pumps air-handling units etc that are essential for the operation of the tower and the comfort of its occupantsBroadcast and Communications Floors
The top four floors have been reserved for communications and broadcasting These floors occupy the levels just below the spire
Main Structure amp DesignThe tower superstructure of Burj Dubai is designed
as an all reinforced concrete building with high performance concrete from the foundation level to level 156 and is topped with a structural steel braced frame from level 156 to the pinnacle
Designers purposely shaped the structural concrete Burj Dubai ndash ldquoYrdquo shaped in plan ndash to reduce the wind forces on the tower as well as to keep the structure simple and foster constructability
The structural system can be described as a ldquobuttressedrdquo core Each wing with its own high performance concrete corridor walls and perimeter columns buttresses the others via a six-sided central core or hexagonal hub
Main Structure amp Design
Structural Analysis amp Design
The top section of the Tower consists of a structural steel spire utilizing a diagonally braced lateral system
The structural steel spire was designed for gravity wind seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999) The exterior exposed steel is protected with a flame applied aluminum finish
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
ArchitectureMechanical Floors
Seven double-storey mechanical floors house the equipment that bring Burj Dubai to life Located every 30 storeys the mechanical floors house the electrical sub-stations water tanks and pumps air-handling units etc that are essential for the operation of the tower and the comfort of its occupantsBroadcast and Communications Floors
The top four floors have been reserved for communications and broadcasting These floors occupy the levels just below the spire
Main Structure amp DesignThe tower superstructure of Burj Dubai is designed
as an all reinforced concrete building with high performance concrete from the foundation level to level 156 and is topped with a structural steel braced frame from level 156 to the pinnacle
Designers purposely shaped the structural concrete Burj Dubai ndash ldquoYrdquo shaped in plan ndash to reduce the wind forces on the tower as well as to keep the structure simple and foster constructability
The structural system can be described as a ldquobuttressedrdquo core Each wing with its own high performance concrete corridor walls and perimeter columns buttresses the others via a six-sided central core or hexagonal hub
Main Structure amp Design
Structural Analysis amp Design
The top section of the Tower consists of a structural steel spire utilizing a diagonally braced lateral system
The structural steel spire was designed for gravity wind seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999) The exterior exposed steel is protected with a flame applied aluminum finish
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Main Structure amp DesignThe tower superstructure of Burj Dubai is designed
as an all reinforced concrete building with high performance concrete from the foundation level to level 156 and is topped with a structural steel braced frame from level 156 to the pinnacle
Designers purposely shaped the structural concrete Burj Dubai ndash ldquoYrdquo shaped in plan ndash to reduce the wind forces on the tower as well as to keep the structure simple and foster constructability
The structural system can be described as a ldquobuttressedrdquo core Each wing with its own high performance concrete corridor walls and perimeter columns buttresses the others via a six-sided central core or hexagonal hub
Main Structure amp Design
Structural Analysis amp Design
The top section of the Tower consists of a structural steel spire utilizing a diagonally braced lateral system
The structural steel spire was designed for gravity wind seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999) The exterior exposed steel is protected with a flame applied aluminum finish
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Main Structure amp Design
Structural Analysis amp Design
The top section of the Tower consists of a structural steel spire utilizing a diagonally braced lateral system
The structural steel spire was designed for gravity wind seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999) The exterior exposed steel is protected with a flame applied aluminum finish
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp Design
The top section of the Tower consists of a structural steel spire utilizing a diagonally braced lateral system
The structural steel spire was designed for gravity wind seismic and fatigue in accordance with the requirements of AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (1999) The exterior exposed steel is protected with a flame applied aluminum finish
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Main Structure amp Design The result is a tower that is
extremely stiff laterally and torsionally similar to a closed tube
Each tier of the building sets back in a spiral stepping pattern up the building The setbacks are organized with the towerrsquos grid such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path
The advantage of the stepping and shaping is to ldquoconfuse the windrdquo The wind vortices never get organized because at each new tier the wind encounters a different building shape
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Main Structure
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp DesignThe center hexagonal walls are
buttressed by the wing walls and hammer head walls which behave as the webs and flanges of a beam to resist the wind shears and moments
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp DesignOutriggers at the mechanical floors
allow the columns to participate in the lateral load resistance of the structure hence all of the vertical concrete is utilized to support both gravity and lateral loads
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp Design Concrete Dimensions
The core walls vary in thickness from 1300mm to 500mm The core walls are typically linked through a series of 800mm to 1100mm deep reinforced concrete or composite link beams at every level
The residential and hotel floor framing system of the Tower consists of 200mm to 300mm two-way reinforced concrete flat plate slabs spanning approximately 9 meters between the exterior columns and the interior core wall
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp Design Link Beams
The demands on the link beams vary greatly
The typical link beams used in the Burj Dubai are quite stocky with a shear-span ratio (l2h) of 085 a width of 650 mm and a height of 825 mm
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp Design Link Beams
For the design of reinforced concrete link beams1 The conventional deep beam design method in
the ACI 318-992 2 Strut-and-tie method in ACI 318-023 were used
with Appendix A enabling the design of link beams somewhat beyond the conventionally designed maximum deep beam stress limit
3 In the case of members subjected to very large shear forces embedded built-up structural steel sections were provided within the core of the concrete link beams to carry the entire shear and flexure demand
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Strut and Tie model for the Link Beam
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Design Details of Link Beams
The geometry factored loads and design methods of four Burj Dubai link beams LB1 to LB4 are shown in Table 1
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Design Details of Link Beams
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp DesignClear Heights
The tower is being constructed utilizing a horizontal compensation program Each story is being constructed incorporating a modest increase in the typical floor-to-floor height
This vertical compensation was selected to ensure the actual height of the structure after the time-dependant shortening effects of creep and shrinkage will be greater than the as-designed final height
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp Design
The structure was analyzed for gravity (including P-Delta analysis) wind and seismic loadings by ETABS version 84
The three-dimensional analysis model consisted of the reinforced concrete walls link beams slabs raft piles and the spire structural steel system
The full 3D analysis model consisted of over73500 shells and 75000 nodes
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp DesignDesign Code
The reinforced concrete structure was designed in accordance with the requirements of ACI 318-02 Building Code Requirements for StructuralConcrete
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp DesignSeismic Loads
bull Dubai is situated towards the eastern edge of the geologically stable Arabian Plate and separated from the unstable Iranian Fold Belt to the north by the Arabian Gulf The site is therefore considered to be located within a seismically active area
bull The Dubai Municipality (DM) specifies Dubai as a UBC97 Zone 2a seismic region with a seismic zone factor Z = 015 and soil profile Sc
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp DesignSeismic Analysis
bull The seismic analysis consisted of a site-specific response spectra analysis
bull Seismic loading typically did not govern the design of the reinforced concrete tower structure But did govern the design of the steel spire
bull Dr Max Irvine developed site-specific seismic reports for the project including a seismic hazard analysis
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Structural Analysis amp DesignDynamic Analysis
bull The dynamic analysis indicated the first mode is lateral sidesway with a period of 113 seconds
bull The second mode is a perpendicular lateral sidesway with a period of 102 seconds
bull Torsion is the fifth mode with a period of 43 seconds
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Types of windWinds that are of interest in the
design of buildings can be classified into three major typesPrevailing Winds (Trade winds)seasonal windslocal winds
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Types of windThe characteristics of the
prevailing and seasonal winds are analytically studied together whereas those of local winds are studied separately
The variations in the speed of prevailing and seasonal winds are referred to as fluctuations in mean velocity The variations in the local winds are referred to as gusts
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
CHARACTERISTICS OF WIND
bull Variation of wind velocity with heightbull Wind turbulencebull Statistical probabilitybull Vortex shedding phenomenonbull Dynamic nature of windndashstructure interaction
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Variation of Wind Velocity with Height
The viscosity of air reduces its velocity adjacent to the earthrsquos surface to almost zero
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Wind TurbulenceFor structural engineering purposes velocity
of wind can be considered as having two components Mean velocity component that increases with
height Turbulent velocity that remains the same over
height
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Probabilistic Approach
In wind engineering the speed of wind is considered to vary with return periods
For example the fastest-mile wind 33 ft (10 m) above ground in Dallas TX corresponding to a 50-year return period(30 ms) compared to the value of (317 ms) for a 100-year recurrence interval
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Vortex SheddingThe flow of wind is simplified and
considered two-dimensionalAlong wind transverse wind
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Vortex SheddingAt low wind speeds shedding
occurs at the same instant on either side of the building It is therefore subject to along-wind oscillations parallel to the wind direction
At higher speeds the vortices are shed alternately first from one and then from the other side there is an impulse in the along-wind direction as before but in addition there is an impulse in the transverse direction
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Wind behavior
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Dynamic Nature of Wind
Wind loads associated with gustiness or turbulence creating effects much larger than if the same loads were applied gradually
Wind loads therefore need to be studied as if they were dynamic in nature
The intensity of a wind load depends on how fast it varies and also on the response of the structure
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
WIND CLIMATE STUDIES In the course of the Burj Dubai studies local
ground based data from several weather stations in the region were used including most importantly the data from Dubai International Airport
Gust data from all stations were merged into the equivalent a super-station to obtain an enlarged database
The 50 year 3 second gust from this analysis was estimated to be 377 ms in standard open terrain at the 10 m level
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
WIND CLIMATE STUDIESIn addition the mean hourly data from Dubai were
used to obtain a model of the parent distribution of hourly winds
This yielded a 50 year mean hourly speed of 235 ms again in standard open terrain conditions at 10 m
Depending on exactly which method one used to estimate the relationship between mean and gust speeds the corresponding gust was estimated to be in the range 357 ms to 376 ms
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
WIND CLIMATE STUDIESAn important question when designing a tower of
over 600 m height is the nature of the wind velocity profile and wind turbulence in the upper levels
It is a large extrapolation to go from ground-based data at the 10 m height to heights of over 600 m using standard assumptions
Therefore for Burj Dubai more direct measurements of upper level winds were sought The closest station with balloon records was Abu Dhabi where about 16 years of data were available taken on average about twice per day
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
WIND CLIMATE STUDIES
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
The Wind Engineering of the Burj Dubai TowerFor a building of this height and
slenderness wind forces and the resulting motions in the upper levels become dominant factors in the structural design
The local wind pressures on the building envelope and the wind speeds around the base of the building and on terraces at various levels were of concern
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
WIND-TUNNEL ENGINEERING
Therefore an extensive program of wind tunnel tests and other studies were undertaken
Rigid pressure model High-frequency force-balance technique Full multi-degree of freedom aeroelastic model
study Measurements of local pressures Pedestrian wind environment studies
bull These studies used models mostly at 1500 scale but for the pedestrian wind studies a larger scale of 1250 was utilized
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Rigid Pressure Model (PM)The primary purpose of the
rigid-model test is for obtaining cladding design pressures get the floor-by-floor shear forces for the design of the overall main wind-force-resisting frame
The wind-tunnel test is run for a duration of about 60 sec which corresponds to approximately 1 hr in real time
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Cladding Pressure Testing
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Cladding Pressure Testing
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
High-Frequency Base Force Balance ModelThe effect of wind load on a flexible
building can be considered as an integrated action resulting from three distinct sourcesThe mean wind load that bends and
twists a buildingThe fluctuating load from the unsteady
nature of the wind that results in oscillation of the building
Inertia forces similar to the lateral forces induced in a building during earthquakes
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
High-Frequency Base Force Balance ModelA rigid model is convenient for
measuring local wind pressures consisting of positive and negative pressures distributed uniquely around a building
These local pressures are integrated to derive net lateral forces in two perpendicular directions and a torsional moment about a vertical axis at each level
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
High-Frequency Base Force Balance ModelThese values have been sufficient
for the design of buildings bracing system
HFBFB ignore the influence of gust factor
It is necessary to assume a conservative gust factor to increase the mean values
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
WIND LOADING ON THE MAIN STRUCTURETo determine the wind loading on the
main structure wind tunnel tests were undertaken early in the design using the high-frequency-force-balance technique
The model itself is rigid and is mounted on a fast response force balance
The technique is that it is relatively quick to undertake and provides the complete spectra of the wind generated modal forces acting on the tower
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
WIND LOADING ON THE MAIN STRUCTURE
The results of the force balance tests were used as early input for the structural design and allowed parametric studies to be undertaken on the effects of varying the towerrsquos stiffness and mass distribution
The wind tunnel data were then combined with the dynamic properties of the tower in order to compute the towerrsquos dynamic response and the overall effective wind force distributions at full scale using aeroelastic model analysis
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
The building has essentially siximportant wind directions
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Orientation of the towerIt was noticed that the force
spectra for different wind directions showed less excitation in the important frequency range for winds impacting the pointed or nose end of a wing than from the opposite direction (tail)
most frequent strong wind directions for Dubai northwest south and east
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
High-Frequency Base Force Balance ModelSeveral rounds of force balance tests
were undertaken as the geometry of the tower evolved and was refined architecturally
After each round of wind tunnel testing the data was analyzed and the building was reshaped to minimize wind effects and accommodate unrelated changes in the Clientrsquos program
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Original Configuration
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Aeroelastic model studyAeroelastic model study attempts
to take the guesswork out of the gust factor computation by measuring directly the magnitude of dynamic loads
The aeroelastic studies require similarity of the inertia stiffness and damping characteristics of the building
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Aeroelastic model studyAeroelastic study basically examines the wind-
induced sway response in addition to providing information on the overall wind-induced mean and dynamic loads
Factors may be used as a guide in making a decision aeroelastic model study
The building height-to-width ratio is greater than about 5 ie the building is slender
Approximate calculations show that there is a likelihood of vortex shedding phenomenon
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Aeroelastic model studyThe structure is light in density on the
order of 8 to 10 lbft3 (125 to 157 kNm3)
The structural stiffness is concentrated in the interior of the building making it torsionally flexible A building with a braced central core is one such example
The calculated period of oscillation of the building is long in excess of 4 or 5 sec
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Aeroelastic model studyIt is more accurate than a force
balance study since the aeroelastic interaction between the structure and wind is fully simulated
Accurate determination of the relationship between peak response and RMS response
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Aeroelastic model studyFor the Burj Dubai the modal
deflection shapes were similar to those of a tapered cantilevered column
Therefore it was possible to obtain excellent agreement between frequencies and mode shapes on the model with those predicted at full scale by using a single machined metal spine in the model with outer shell segments attached to it
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Aeroelastic model studyThe aeroelastic model was able
to model the first six sway modes Bending moments were measured at the base as well as at several higher levels Accelerations were also measured in the upper levels
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Comparing aeroelastic model test results force balance resultsIt was found that the base
moment and the accelerations in the upper levels were significantly lower in the aeroelastic model results
Part of this was identified as a Reynolds number effect because the force balance tests had been run at lower Reynolds number
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Comparing aeroelastic model test results force balance results
Differences between the force balance method and the aeroelastic method on Burj Dubai
Due to approximations in the force balance procedure as applied to a highly tapered towered
Force balance method keep model resonance frequencies high enough to avoid them interfering with the frequency range of interest and one solution is to run at lower tunnel wind speeds which entails reducing the Reynolds number
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
BUILDING MOTIONSBased on the High-Frequency-Force-Balance
test results combined with local wind statistics the building motions in terms of peak accelerations were predicted for various return periods in the 1 to 10 year range
Initial predictions obtained in May 2003 at over 37 milli-g for the 5 year return period
By the end of 2004 November 2003 they had come down to about 19 milli-g for the same return period
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
BUILDING MOTIONSHalf of this improvement came about as
a result of improved knowledge of the wind statistics and the rest through re-orientation structural improvements and shape adjustments
Several variations of tower height were tested using aeroelastic models
The accelerations were reduced to the range of 12 milli-g
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Human Response to Building Motions
Building motion under the action of wind is a serviceability issue
A commonly used criterion is to limit the acceleration of a buildingrsquos upper floors to no more than 20 of gravity (20 mg) for a 10-year return period
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
PEDESTRIAN WIND STUDIES
A sheet of air moving over the earthrsquos surface is reluctant to rise when it meets an obstacle such as a tall building it prefers to flow around the building rather than over it
Wind is driven in two directions Some of it will be deflected upward but most of it will spiral to the ground creating a so-called standing vortex or mini tornado at sidewalk level
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
PEDESTRIAN WIND STUDIES
Smooth-skinned skyscrapers may be subjected to what is called the Mary Poppins syndrome referring to the tendency of the wind to lift the pedestrian literally off his or her feet
Another effect known as the Marilyn Monroe effect refers to the billowing action of womenrsquos skirts in the turbulence of wind around and in the vicinity of a building
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
PEDESTRIAN WIND STUDIES
The comfort of pedestrians at ground level and on the numerous terrace levels was evaluated by combining wind speed measurements on wind tunnel models with the local wind statistics and other climatic information
Two aspects of pedestrian comfort were considered the effect of the mechanical force of the wind thermal comfort
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
PEDESTRIAN WIND STUDIES
Initial wind tunnel tests used 1500 scale models
Subsequently three 1250 scale partial models were employed to examine ground level areas
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Foundations
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Soil InvestigationHyder Consulting (UK) Ltd (HCL) were appointed geotechnical consultant for the works by Emaar and carried out the design of the foundation system
Soil Investigation in 4 stages includedbull 23 boreholesbull in situ SPTrsquosbull 40 pressuremeter tests in 3 boreholes bull installation of 4 standpipe piezometers bull laboratory testing specialist laboratory testing and
contamination testingbull 3 geophysical boreholes with cross-holebull tomography geophysical surveys
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Soil Investigationbull The quality of core recovered in some of
the earlier boreholes was somewhat poorer than that recovered in later boreholes
bull therefore the defects noted in the earlier rock cores may not have been representative of the actual defects present in the rock mass
bull Phase 4 of the investigation was targeted to assess the difference in core quality and this indicated that the differences were probably related to the drilling fluid used and the overall quality of drilling
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Soil Investigation amp Ground Waterbull The groundwater in which the Burj Dubai
substructure is constructed is particularly severe
bull The chloride and sulfate concentrations found in the groundwater are even higher than the concentrations in sea water
bull Measures implemented include specialized waterproofing systems1 Increased concrete cover2 Addition of corrosion inhibitors to the
concrete mix3 Stringent crack control design criteria
and 4 Impressed current cathodic protection
system utilizing titanium mesh 5 A controlled permeability formwork
liner
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Ground Water amp Concrete Mix
bull A specially designed concrete mix was formulated to resist attack from the ground water
bull The concrete mix for the piles was a 60 MPa mix based on a triple blend with 25 fly ash 7 silica fume and a water to cement ratio of 032
bull The concrete was also designed as a fully self consolidating concrete A robust cathodic protection system for both the bored piles and the raft foundation
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
PilesThe Tower raft is supported by 194 boredcast-
in-place piles15m diameter and 4745m long with the
tower raft founded at -755mThe C60 (cube strength) SCC concrete was
placed by the tremie method utilizing polymer slurry When the rebar cage was placed in the piles special attention was paid to orient the rebar cage such that the raft bottom rebar could be threaded through the numerous pile rebar cages without interruption which greatly simplified the raft construction
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Pile Testing1 Static load tests on seven trial piles
prior to foundation construction 2 Static load tests on eight works piles
carried out during the foundation construction phase (ie on about 1 of the total number of piles constructed)
3 In addition dynamic pile testing was carried out on 10 of the works piles for the tower and 31 piles for the podium ie on about 5 of the total works piles
4 Sonic integrity testing was also carried out on a number of the works piles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Static Testing on trial pilesThe main purpose of the tests was to assess
the general load-settlement behaviour of piles of the anticipated length below the tower and to verify the design assumptions Each of the test piles was different allowing various factors to be investigated as follows
1 The effects of increasing the pile shaft length2 The effects of shaft grouting3 The effects of reducing the shaft diameter4 The effects of uplift (tension) loading5 The effects of lateral loading6 The effect of cyclic loading
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Static Working Pile TestThe Tower raft is supported by 194
bored cast-in-place piles The piles are 15 meter in diameter and approximately 43 meters long with a design capacity of 3000 ton each
The Tower pile load test supported over 6000 ton
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Settlement It was determined the maximum
long-term settlement over time would be about a maximum of 80mm
This settlement would be a gradual curvature of the top of grade over the entire large site When the construction was at Level 135 the average foundation settlement was 30mm
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Construction Achieve a three (3) day-cycle for structural
worksDevelop optimum transportation systems
with large capacity high speed equipmentUtilize optimum formwork system to
accommodate various building shapes along the building height
Develop organized logistic plans throughout the construction period
Apply all high-rise construction technologies available at the time of construction
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Planning for the concrete workbull Prior to the construction of the tower
extensive concrete testing and quality control programs were put in place to ensure that all concrete works are done in agreement with all parties involved
bull Tests are needed to confirm the construction sequence of these large elements and to develop curing plans that are appropriate for the project considering major daily and seasonal temperature fluctuations
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Testing Regimes for Concretebull Trial mix designs for all concrete types needed for the
projectbull Mechanical properties including compressive strength
modulus of elasticity and split tensile strengthbull Durability tests which included initial surface
absorption test and 30 minute absorption testbull Creep and shrinkage test program for all concrete mix
designbull Water penetration tests and rapid chloride permeability
testbull Shrinkage test program for all concrete mix designsbull Pump simulation test for all concrete mix design grades
up to at least 600 metersbull Heat of hydration analysis and tests
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Testing Regimes for Concretebull Creep Test
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Testing Regimes for Concrete
bull Pump Simulation Test using over 600m of pipe length to confirm the pump capacity and evaluate the overall pressure losses in the pipes due to friction connections concrete type
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Testing Regimes for Concretebull Pump Simulation
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Testing Regimes for Concretebull Heat of Hydration Make-op Test
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Technologies used to achieve 3-day cycles
bull Auto Climbing formwork system (ACS)bull Rebar pre-fabricationbull High performance concrete suitable for
providing high strength high durability requirement high modulus and pumping
bull Advanced concrete pumping technologybull Simple drop head formwork system that
can be dismantled and assembled quickly with minimum labor requirements
bull ColumnWall proceeding method part of ACS formwork system
Technologies used to achieve 3-day cycles
Technologies used to achieve 3-day cycles
Sequence of Construction and ACSThe ACS form work is divided into four sections consisting of the center core wall that is followed by the wing wall construction along each of the three tower wings
Sequence of Construction and ACS
Sequence of Construction and ACS
Rebar Pre-fabrication bull Most of the reinforcing
bars for the core walls wing walls and the nose columns were prefabricated at the ground level
bull This rebar fabrication and pre-assembly method resulted in man quality control advantages and reduced the number of workers going up and down the tower
bull The rebar was assembled in double story modules to speed up the vertical element construction time
Slab Formwork SystemDrop head system (also known as slab support system is specially designed to sustain a large combination of grid sizes resulting in maximum reusability of formwork amp economy) used for the slab construction
Slab Formwork SystemThe slab shoring system consists of four levels of shores and one level of re-shore to control the maximum loads in the slabs at the lowest level However the shoring props at the upper-most slab were left undisturbed
Day 0
Conrsquoc Pouring
Day 1
Slab formwork
Day 2
Slab formwork
Rebar Installation
MEP
Day 3
Conrsquoc Pouring
13 of Prop
23 of Prop
Form
23 of Prop
12 of Raking Shore
Form Form
12 of Raking Shore
23 of Prop
12 of Raking Shore
N-1
N-2
N-3
N-4
N-5
N+0
Additional Raking Shore
N+1
Form
Concrete Pumping
CPB1CPB3
CPB4
CPB2
Level Height Pouring Method Remarks
Ground ~ L145 531 m Direct PumpingTarget Height (RC Structure)
L146 ~ L160M 624 m Re-pumpingSecondary Pump on
L124 (East wing 442m)
L160M ~ Spire1 6817 m Hopper by TC From Ground Level
Level Pressure OutputEngin
eRemarks
Pump1~3
185 320 bar
71 36 m3hr
470 kw
2 nos of Main1 no of Stand by
Pump4220 260 bar
110 m3hr200 kw
SecondaryPumping
Pumping Area (Ground Level)
Pipe Lines
Concrete Pump
Pipe Lines
- D150mm THK 11mm- 5 Lines (1 for back up)
Concrete Placing Boom
- 32m boom for Center Core- 3nos of 28m boom for Wing Core
Concrete Pumping
TIER 24 FINIAL HIGH
TOF
TIER 23 FINIAL MID
TIER 22 FINIAL LOW
TIER 21 SPIRE L5TIER 20 SPIRE L4
TIER 19 SPIRE L3
TIER 18 SPIRE L2
TIER 17 LEVEL 161
TIER 16 LEVEL 158
TIER 15 LEVEL 155
TIER 14 LEVEL 151
TIER 13 LEVEL 147
TIER 12 LEVEL 142
TIER 11 LEVEL 126
TIER 10 LEVEL 112
TIER 9 LEVEL 99
TIER 8 LEVEL 87
TIER 7 LEVEL 76
TIER 6 LEVEL 64
TIER 5 LEVEL 53
TIER 4 LEVEL 43
TIER 3 LEVEL 34
TIER 2 LEVEL 26
TIER 1 LEVEL 19
TIER 0 LEVEL 7
Line2 (L139)for South Wing
Line3 (L124)for East Wing
Line4 (L112)for West Wing
Pump4 (Secondary Pump on L124)
Line1 (L160) for Center Core
Line5 (L160) for Back up
L154 RC Structure
L160Mezzanine Steel Structure
Top of Finial Spire
Pinnacle
Pumping AreaPump1~3
Pipe Lines
- D150mm THK 11mm- 5 Lines (1 for back up)
Concrete Pumping
Concrete Pumping
Slab Formwork SystemDrop head system (also known as slab support system is specially designed to sustain a large combination of grid sizes resulting in maximum reusability of formwork amp economy) used for the slab construction
Slab Formwork SystemThe slab shoring system consists of four levels of shores and one level of re-shore to control the maximum loads in the slabs at the lowest level However the shoring props at the upper-most slab were left undisturbed
Day 0
Conrsquoc Pouring
Day 1
Slab formwork
Day 2
Slab formwork
Rebar Installation
MEP
Day 3
Conrsquoc Pouring
13 of Prop
23 of Prop
Form
23 of Prop
12 of Raking Shore
Form Form
12 of Raking Shore
23 of Prop
12 of Raking Shore
N-1
N-2
N-3
N-4
N-5
N+0
Additional Raking Shore
N+1
Form
Concrete Pumping
CPB1CPB3
CPB4
CPB2
Level Height Pouring Method Remarks
Ground ~ L145 531 m Direct PumpingTarget Height (RC Structure)
L146 ~ L160M 624 m Re-pumpingSecondary Pump on
L124 (East wing 442m)
L160M ~ Spire1 6817 m Hopper by TC From Ground Level
Level Pressure OutputEngin
eRemarks
Pump1~3
185 320 bar
71 36 m3hr
470 kw
2 nos of Main1 no of Stand by
Pump4220 260 bar
110 m3hr200 kw
SecondaryPumping
Pumping Area (Ground Level)
Pipe Lines
Concrete Pump
Pipe Lines
- D150mm THK 11mm- 5 Lines (1 for back up)
Concrete Placing Boom
- 32m boom for Center Core- 3nos of 28m boom for Wing Core
Concrete Pumping
TIER 24 FINIAL HIGH
TOF
TIER 23 FINIAL MID
TIER 22 FINIAL LOW
TIER 21 SPIRE L5TIER 20 SPIRE L4
TIER 19 SPIRE L3
TIER 18 SPIRE L2
TIER 17 LEVEL 161
TIER 16 LEVEL 158
TIER 15 LEVEL 155
TIER 14 LEVEL 151
TIER 13 LEVEL 147
TIER 12 LEVEL 142
TIER 11 LEVEL 126
TIER 10 LEVEL 112
TIER 9 LEVEL 99
TIER 8 LEVEL 87
TIER 7 LEVEL 76
TIER 6 LEVEL 64
TIER 5 LEVEL 53
TIER 4 LEVEL 43
TIER 3 LEVEL 34
TIER 2 LEVEL 26
TIER 1 LEVEL 19
TIER 0 LEVEL 7
Line2 (L139)for South Wing
Line3 (L124)for East Wing
Line4 (L112)for West Wing
Pump4 (Secondary Pump on L124)
Line1 (L160) for Center Core
Line5 (L160) for Back up
L154 RC Structure
L160Mezzanine Steel Structure
Top of Finial Spire
Pinnacle
Pumping AreaPump1~3
Pipe Lines
- D150mm THK 11mm- 5 Lines (1 for back up)
Concrete Pumping
Concrete Pumping
Slab Formwork SystemThe slab shoring system consists of four levels of shores and one level of re-shore to control the maximum loads in the slabs at the lowest level However the shoring props at the upper-most slab were left undisturbed
Day 0
Conrsquoc Pouring
Day 1
Slab formwork
Day 2
Slab formwork
Rebar Installation
MEP
Day 3
Conrsquoc Pouring
13 of Prop
23 of Prop
Form
23 of Prop
12 of Raking Shore
Form Form
12 of Raking Shore
23 of Prop
12 of Raking Shore
N-1
N-2
N-3
N-4
N-5
N+0
Additional Raking Shore
N+1
Form
Concrete Pumping
CPB1CPB3
CPB4
CPB2
Level Height Pouring Method Remarks
Ground ~ L145 531 m Direct PumpingTarget Height (RC Structure)
L146 ~ L160M 624 m Re-pumpingSecondary Pump on
L124 (East wing 442m)
L160M ~ Spire1 6817 m Hopper by TC From Ground Level
Level Pressure OutputEngin
eRemarks
Pump1~3
185 320 bar
71 36 m3hr
470 kw
2 nos of Main1 no of Stand by
Pump4220 260 bar
110 m3hr200 kw
SecondaryPumping
Pumping Area (Ground Level)
Pipe Lines
Concrete Pump
Pipe Lines
- D150mm THK 11mm- 5 Lines (1 for back up)
Concrete Placing Boom
- 32m boom for Center Core- 3nos of 28m boom for Wing Core
Concrete Pumping
TIER 24 FINIAL HIGH
TOF
TIER 23 FINIAL MID
TIER 22 FINIAL LOW
TIER 21 SPIRE L5TIER 20 SPIRE L4
TIER 19 SPIRE L3
TIER 18 SPIRE L2
TIER 17 LEVEL 161
TIER 16 LEVEL 158
TIER 15 LEVEL 155
TIER 14 LEVEL 151
TIER 13 LEVEL 147
TIER 12 LEVEL 142
TIER 11 LEVEL 126
TIER 10 LEVEL 112
TIER 9 LEVEL 99
TIER 8 LEVEL 87
TIER 7 LEVEL 76
TIER 6 LEVEL 64
TIER 5 LEVEL 53
TIER 4 LEVEL 43
TIER 3 LEVEL 34
TIER 2 LEVEL 26
TIER 1 LEVEL 19
TIER 0 LEVEL 7
Line2 (L139)for South Wing
Line3 (L124)for East Wing
Line4 (L112)for West Wing
Pump4 (Secondary Pump on L124)
Line1 (L160) for Center Core
Line5 (L160) for Back up
L154 RC Structure
L160Mezzanine Steel Structure
Top of Finial Spire
Pinnacle
Pumping AreaPump1~3
Pipe Lines
- D150mm THK 11mm- 5 Lines (1 for back up)
Concrete Pumping
Concrete Pumping
Concrete Pumping
CPB1CPB3
CPB4
CPB2
Level Height Pouring Method Remarks
Ground ~ L145 531 m Direct PumpingTarget Height (RC Structure)
L146 ~ L160M 624 m Re-pumpingSecondary Pump on
L124 (East wing 442m)
L160M ~ Spire1 6817 m Hopper by TC From Ground Level
Level Pressure OutputEngin
eRemarks
Pump1~3
185 320 bar
71 36 m3hr
470 kw
2 nos of Main1 no of Stand by
Pump4220 260 bar
110 m3hr200 kw
SecondaryPumping
Pumping Area (Ground Level)
Pipe Lines
Concrete Pump
Pipe Lines
- D150mm THK 11mm- 5 Lines (1 for back up)
Concrete Placing Boom
- 32m boom for Center Core- 3nos of 28m boom for Wing Core
Concrete Pumping
TIER 24 FINIAL HIGH
TOF
TIER 23 FINIAL MID
TIER 22 FINIAL LOW
TIER 21 SPIRE L5TIER 20 SPIRE L4
TIER 19 SPIRE L3
TIER 18 SPIRE L2
TIER 17 LEVEL 161
TIER 16 LEVEL 158
TIER 15 LEVEL 155
TIER 14 LEVEL 151
TIER 13 LEVEL 147
TIER 12 LEVEL 142
TIER 11 LEVEL 126
TIER 10 LEVEL 112
TIER 9 LEVEL 99
TIER 8 LEVEL 87
TIER 7 LEVEL 76
TIER 6 LEVEL 64
TIER 5 LEVEL 53
TIER 4 LEVEL 43
TIER 3 LEVEL 34
TIER 2 LEVEL 26
TIER 1 LEVEL 19
TIER 0 LEVEL 7
Line2 (L139)for South Wing
Line3 (L124)for East Wing
Line4 (L112)for West Wing
Pump4 (Secondary Pump on L124)
Line1 (L160) for Center Core
Line5 (L160) for Back up
L154 RC Structure
L160Mezzanine Steel Structure
Top of Finial Spire
Pinnacle
Pumping AreaPump1~3
Pipe Lines
- D150mm THK 11mm- 5 Lines (1 for back up)
Concrete Pumping
Concrete Pumping
Concrete Pumping
TIER 24 FINIAL HIGH
TOF
TIER 23 FINIAL MID
TIER 22 FINIAL LOW
TIER 21 SPIRE L5TIER 20 SPIRE L4
TIER 19 SPIRE L3
TIER 18 SPIRE L2
TIER 17 LEVEL 161
TIER 16 LEVEL 158
TIER 15 LEVEL 155
TIER 14 LEVEL 151
TIER 13 LEVEL 147
TIER 12 LEVEL 142
TIER 11 LEVEL 126
TIER 10 LEVEL 112
TIER 9 LEVEL 99
TIER 8 LEVEL 87
TIER 7 LEVEL 76
TIER 6 LEVEL 64
TIER 5 LEVEL 53
TIER 4 LEVEL 43
TIER 3 LEVEL 34
TIER 2 LEVEL 26
TIER 1 LEVEL 19
TIER 0 LEVEL 7
Line2 (L139)for South Wing
Line3 (L124)for East Wing
Line4 (L112)for West Wing
Pump4 (Secondary Pump on L124)
Line1 (L160) for Center Core
Line5 (L160) for Back up
L154 RC Structure
L160Mezzanine Steel Structure
Top of Finial Spire
Pinnacle
Pumping AreaPump1~3
Pipe Lines
- D150mm THK 11mm- 5 Lines (1 for back up)
Concrete Pumping
Concrete Pumping
Concrete Pumping
Concrete Pumping
Concrete Pumping
Spire Erection and Pinnacle Assemblybull At Level 156 the reinforced concrete core wall
will reach its highest point and serves as the foundation for the spirersquos structural steel works
bull The central pinnacle structure which consists of 1200mm-2100mm diameter structural steel pipe varies in thickness from 60mm at the lowest level to 30mm at the top
bull The erection of the spire and the pinnacle starts from level 156 and the erection of the spire was done in traditional steel construction method However the pinnacle pipe sections are stacked from level 156 and lifted to the final position from within the spire
Spire Erection and Pinnacle AssemblyThe sequence of the pinnacle installation is shown in Figure below and as follows
bull Erection of the spire structurebull Installation of the support beambull Installation of the lifting block and assembliesbull Installation of the lifting equipment and
assembliesbull Lifting the pinnacle in a three step processbull Installing cladding after each liftbull Completing lift of the pinnacle and all connection
connections (gravity and lateral)bull Completion of the cladding installation
Spire Erection and Pinnacle Assembly
Spire Erection and Pinnacle AssemblyThe sequence of the pinnacle installation is shown in Figure below and as follows
bull Erection of the spire structurebull Installation of the support beambull Installation of the lifting block and assembliesbull Installation of the lifting equipment and
assembliesbull Lifting the pinnacle in a three step processbull Installing cladding after each liftbull Completing lift of the pinnacle and all connection
connections (gravity and lateral)bull Completion of the cladding installation
Spire Erection and Pinnacle Assembly
Spire Erection and Pinnacle Assembly
Survey amp Monitoring
bull Low Level Tower Control (Classical Control Method )
XYZ
XYZ
XYZ
XYZ
Survey amp Monitoring bull Hight Level Tower Control (GPS
Real Time Kinematic)
Survey amp Monitoring bull Hight Level Tower Control (GPS
Real Time Kinematic)
EvacuationBurj Dubai has built in fire protection as its concrete back bone is naturally fire resistantBut how will people go out in an emergencyThe answer they donrsquot bull The burj dubai contains 9 special rooms build
throw layers of reinforced concrete and fire proof sheeting
bull The walls of these rooms will stand the heat of a fire for 2 hours
bull Each room has special supply of air pumped throw fire resistant pipes sealed fire proofed doors stop smoke from leaking in
Evacuationbull There is 1 of these rooms in about every 30 floors How they prevent the smoke from blocking the
access route to the roomsbull Early warning system
bull Fire activate a smoke detectorbull Heat sensorbull Water sprinklersbull Net work of high power fans kick inbull Fans force new clean cool air throw fire
resistant ducts into the buildingbull The fresh air pushes the smoke out of the
stair way keeping the evacuation route clear
Evacuation
Evacuationbull There is 1 of these rooms in about every 30 floors How they prevent the smoke from blocking the
access route to the roomsbull Early warning system
bull Fire activate a smoke detectorbull Heat sensorbull Water sprinklersbull Net work of high power fans kick inbull Fans force new clean cool air throw fire
resistant ducts into the buildingbull The fresh air pushes the smoke out of the
stair way keeping the evacuation route clear
Evacuation
Evacuation
Cladding bull 30000 glass panels of high quality European
glass enough to cover 17 football fields
bull The glass is thicker at the top to resist the high wind
bull Its designed to let the maximum light in and to keep heat out
Sun screen (inside face) is useless against infrared
from the hot desert sun so the inner plan is coated
with a thin layer of silver that keeps the heat rays
out
Outside coat reflects the daily solar heat comes direct from the
sun
The metal coating deflects UV Radiation that will otherwise heat
up the building
Cladding Test 1 Air infiltration test To measure how much air gets in through the joints
Test 2 static water test bull Water is spread
evenly for 15 minutes from nozles attached to the glass
bull Transducers measures how much water gets in
bull The data is transferred to computer for analysis
Cladding Test 1 Air infiltration test To measure how much air gets in through the joints
Test 2 static water test bull Water is spread
evenly for 15 minutes from nozles attached to the glass
bull Transducers measures how much water gets in
bull The data is transferred to computer for analysis
Cladding Test 3 Dynamic water Test
bull Itrsquos a simulation for a desert ndash Storm
bull The wind is Generated by a giant Fan and its Spread water against the glass for 15 minutes
Cladding Test 4 Earthquake Test
bull Earthquake Simulation which move the mock-up floor of curtain walls 10 mm in two directions
bull With this test the know that curtain wall wonrsquot break
Faccedilade Maintenance bull The towers primary window washing and facade
maintenance system consists of three permanently-installed track-mounted telescopic building maintenance machines located in internal garage positions on uppermost levels
bull it will take 36 workers three to four months to clean the entire exterior facade
Elevatorsbull With an lsquointelligent
elevator installationrsquo mechanism builders of Burj Dubai ensure a speedy journey from the ground to the 160th floor
bull 57 elevators and eight escalators to streamline the needs of the residents and visitors to commute within the tower These elevators mark the highest installation in any building and have been developed by Otis
Elevatorsbull The main service
elevator that is positioned in the central core of Burj Dubai has the worldrsquos highest elevator rise at 504 metres
bull It moves at a speed of 9 metres per second and also has the worldrsquos longest travelling distance for an elevator The lift to the spire has the worldrsquos highest landing at 6369 meters
Elevatorsbull The main service
elevator that is positioned in the central core of Burj Dubai has the worldrsquos highest elevator rise at 504 metres
bull It moves at a speed of 9 metres per second and also has the worldrsquos longest travelling distance for an elevator The lift to the spire has the worldrsquos highest landing at 6369 meters
Elevatorsbull Elevators are placed into
different zones Each elevator zone serves different audiences maximizing the efficiency and saving time
bull The sky lobby is an intermediate floor where residents guests office staff will change from an express elevator to a local elevator which stops at each floor within a certain segment of the building The sky lobbies are located on level 43 76 and 123 and will include a lounge area
Thank YouMosatafa atteya Ahmed Essam Ramez Nazir
Mohamed Salah
- Burj Dubai Concept Design amp Construction
- Introduction
- Worldrsquos Tallest Building
- Worldrsquos Tallest Building (2)
- Architectural Concept
- Architecture
- Architecture (2)
- Architecture (3)
- Slide 9
- Main Structure amp Design
- Main Structure amp Design (2)
- Structural Analysis amp Design
- Main Structure amp Design (3)
- Main Structure
- Structural Analysis amp Design (2)
- Structural Analysis amp Design (3)
- Structural Analysis amp Design Concrete Dimensions
- Structural Analysis amp Design Link Beams
- Structural Analysis amp Design Link Beams (2)
- Strut and Tie model for the Link Beam
- Design Details of Link Beams
- Design Details of Link Beams (2)
- Structural Analysis amp Design Clear Heights
- Structural Analysis amp Design (4)
- Structural Analysis amp Design Design Code
- Structural Analysis amp Design Seismic Loads
- Structural Analysis amp Design Seismic Analysis
- Structural Analysis amp Design Dynamic Analysis
- Types of wind
- Types of wind (2)
- CHARACTERISTICS OF WIND
- Variation of Wind Velocity with Height
- Wind Turbulence
- Probabilistic Approach
- Vortex Shedding
- Vortex Shedding (2)
- Wind behavior
- Dynamic Nature of Wind
- WIND CLIMATE STUDIES
- WIND CLIMATE STUDIES (2)
- WIND CLIMATE STUDIES (3)
- WIND CLIMATE STUDIES (4)
- The Wind Engineering of the Burj Dubai Tower
- WIND-TUNNEL ENGINEERING
- Rigid Pressure Model (PM)
- Slide 46
- Cladding Pressure Testing
- Cladding Pressure Testing (2)
- High-Frequency Base Force Balance Model
- High-Frequency Base Force Balance Model (2)
- High-Frequency Base Force Balance Model (3)
- WIND LOADING ON THE MAIN STRUCTURE
- WIND LOADING ON THE MAIN STRUCTURE (2)
- The building has essentially six important wind directions
- Orientation of the tower
- High-Frequency Base Force Balance Model (4)
- Original Configuration
- Slide 58
- Aeroelastic model study
- Slide 60
- Aeroelastic model study (2)
- Aeroelastic model study (3)
- Aeroelastic model study (4)
- Aeroelastic model study (5)
- Aeroelastic model study (6)
- Comparing aeroelastic model test results force balance results
- Comparing aeroelastic model test results force balance results (2)
- Slide 68
- BUILDING MOTIONS
- BUILDING MOTIONS (2)
- Human Response to Building Motions
- PEDESTRIAN WIND STUDIES
- PEDESTRIAN WIND STUDIES (2)
- PEDESTRIAN WIND STUDIES (3)
- PEDESTRIAN WIND STUDIES (4)
- Foundations
- Soil Investigation
- Soil Investigation (2)
- Soil Investigation amp Ground Water
- Ground Water amp Concrete Mix
- Piles
- Pile Testing
- Static Testing on trial piles
- Static Working Pile Test
- Settlement
- Slide 86
- Planning for the concrete work
- Testing Regimes for Concrete
- Testing Regimes for Concrete (2)
- Testing Regimes for Concrete (3)
- Testing Regimes for Concrete (4)
- Testing Regimes for Concrete (5)
- Technologies used to achieve 3-day cycles
- Technologies used to achieve 3-day cycles (2)
- Sequence of Construction and ACS
- Sequence of Construction and ACS (2)
- Rebar Pre-fabrication
- Slab Formwork System
- Slab Formwork System (2)
- Concrete Pumping
- Concrete Pumping (2)
- Concrete Pumping (3)
- Concrete Pumping (4)
- Spire Erection and Pinnacle Assembly
- Spire Erection and Pinnacle Assembly (2)
- Spire Erection and Pinnacle Assembly (3)
- Survey amp Monitoring
- Survey amp Monitoring (2)
- Evacuation
- Evacuation (2)
- Evacuation (3)
- Cladding
- Cladding (2)
- Cladding (3)
- Cladding (4)
- Faccedilade Maintenance
- Elevators
- Elevators (2)
- Elevators (3)
- Slide 120
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