MultiMulti--storey storey structural Steel Structures structural Steel Structures

BackgroundBackgroundSteel has been used for constructing buildings in the western Steel has been used for constructing buildings in the western

world for more than 150 years. With the introduction of world for more than 150 years. With the introduction of standard sections by the end of 19standard sections by the end of 19thth Century, steel Century, steel structures were getting much more popular as a choice of structures were getting much more popular as a choice of construction for highconstruction for high--rise buildings.rise buildings.

The use of structural steel to construct started only in the 70The use of structural steel to construct started only in the 70’’s s in HK, below is some of the projects being completed:in HK, below is some of the projects being completed:

1.1. Park Lane Hotel (Causeway Bay, 1972)Park Lane Hotel (Causeway Bay, 1972)2.2. Grand Hyatt & Harbor View Hotel (HKCEC Phase I, 1990)Grand Hyatt & Harbor View Hotel (HKCEC Phase I, 1990)3.3. Bank of China Tower (Central, 1991)Bank of China Tower (Central, 1991)4.4. Time Square (Causeway Bay, 1992)Time Square (Causeway Bay, 1992)5.5. Lee Garden Redevelopment (ManuLee Garden Redevelopment (Manu--life Tower, 1997)life Tower, 1997)6.6. The Center (Central, 1999)The Center (Central, 1999)7.7. Cheung Kong Center (Central, 2000)Cheung Kong Center (Central, 2000)

Properties of steel Properties of steel -- Steel has the following Steel has the following properties, that makes it one of the most efficient properties, that makes it one of the most efficient materials for use in building construction.materials for use in building construction.

Favorable propertiesFavorable properties-- Strong: has a high strength/weight ratioStrong: has a high strength/weight ratio-- Versatility: adaptable and ductileVersatility: adaptable and ductile-- Cheap and plentifulCheap and plentiful-- Easy to cut, connect and fabricateEasy to cut, connect and fabricateSome drawbacksSome drawbacks-- Heavy and lengthy, not easy to handleHeavy and lengthy, not easy to handle-- Loss strength under higher temperatureLoss strength under higher temperature-- Easily get rust if not properly treatedEasily get rust if not properly treated-- Deflect under loadsDeflect under loads

The use of structural steel sectionsThe use of structural steel sections

The availability of steel sections in a variety The availability of steel sections in a variety of dimensional ranges provides the of dimensional ranges provides the designers with a wide variety of design designers with a wide variety of design options.options.

These sections are manufactured in These sections are manufactured in convenient shapes, sizes and thickness. convenient shapes, sizes and thickness. They can be readily fabricated, They can be readily fabricated, combined and connected to form combined and connected to form unlimited possibility of designsunlimited possibility of designs

Standard structural steel sectionsStandard structural steel sections

Typical jointing details for structural frameTypical jointing details for structural frame

Column Column connects to baseconnects to base

Typical jointing details for structural frameTypical jointing details for structural frame

Connecting HConnecting H--column to form continual columncolumn to form continual column

Using splice plate

Using welded joint

Typical jointing details for structural frameTypical jointing details for structural frame

Connecting beam to column

Connecting beam to beam

Typical layout of structural frameTypical layout of structural frame

Simple cage frame cantilever frame

Typical layout of structural frameTypical layout of structural frame

Propped cantilever frame

Typical layout of structural frameTypical layout of structural frame

Wind-braced structures

Typical layout of structural frameTypical layout of structural frame

Core structure

Characteristic of various kinds of structural Characteristic of various kinds of structural steel framed structuressteel framed structuresIn general, the performance of steel frame In general, the performance of steel frame

structure may be affected by the following structure may be affected by the following factorsfactors

a)a) Length of spanLength of spanb)b) Composition/continuity of spanComposition/continuity of spanc)c) Methods of jointing the membersMethods of jointing the membersd)d) Movement and deflection allowedMovement and deflection allowedWhen using in When using in lowhaslowhas very good and efficient.very good and efficient.Favorable properties of steelFavorable properties of steel-- Strong: has a high strength/weight Strong: has a high strength/weight ratioentifulratioentiful-- Easy to cut, connect and Easy to cut, connect and fabricatefabricategetget rust if not rust if not

properly treatedproperly treated

Principle factors affecting choice of framePrinciple factors affecting choice of frame

Structural Design considerationStructural Design considerationnn Foundation considerationFoundation considerationnn Standardization of members or designStandardization of members or designnn Span and floor loadsSpan and floor loadsnn Fire resistance requirementFire resistance requirementnn Maintenance considerationMaintenance considerationnn Integration of architectural & structural elementsIntegration of architectural & structural elements

Features of structural steel construction Features of structural steel construction Structural characteristicsStructural characteristics1.1. Steel has lower dead load (unless encased in Steel has lower dead load (unless encased in

concrete)concrete)2.2. Steel frame can easily to have the layout changed to Steel frame can easily to have the layout changed to

suit new design than concrete, especially requiring suit new design than concrete, especially requiring alteration after completion of the building.alteration after completion of the building.

3.3. Easily accommodate building movements for steel is Easily accommodate building movements for steel is a relatively flexible material and have greater a relatively flexible material and have greater adaptability to take up strain and deformationadaptability to take up strain and deformation

4.4. However, it is weaker in fire resistance for steel will However, it is weaker in fire resistance for steel will lose strength and deform serious at higher lose strength and deform serious at higher temperature (at 600temperature (at 600ooC or above). This can be C or above). This can be improved by applying fire resistant plasterimproved by applying fire resistant plaster

Features of structural steel construction Features of structural steel construction Structural characteristics (continue)Structural characteristics (continue)5.5. Beams usually shallower in size than for concrete Beams usually shallower in size than for concrete

BeamsBeams6.6. Sections in various convenient type and size thus Sections in various convenient type and size thus

economical in design and uses economical in design and uses –– refer to standard refer to standard steel sectionssteel sections

7.7. Produce larger deflection & deformation (Bend) Produce larger deflection & deformation (Bend) under wind under wind –– this will cause this will cause uncomfortuncomfort to users of to users of buildingbuilding

8.8. Steel has higher thermal expansion valueSteel has higher thermal expansion value9.9. Rusting or corrosion problems Rusting or corrosion problems –– very strict antivery strict anti--

corrosion treatment has to be appliedcorrosion treatment has to be applied

Features of structural steel construction (cont.)Features of structural steel construction (cont.)Construction aspectsConstruction aspects1.1. Quicker to erect and can be prepared offsite Quicker to erect and can be prepared offsite –– in in

workshop/factory environment with good workshop/factory environment with good production and quality controlproduction and quality control

2.2. Erection on site less affected by climatic Erection on site less affected by climatic conditions conditions –– without placing of concretewithout placing of concrete

3.3. Longer and highly coordinated planning Longer and highly coordinated planning –– require require long time to make structural design, fabrication long time to make structural design, fabrication and deliveryand delivery

4.4. Higher requirement in the control of dimensional Higher requirement in the control of dimensional accuracy before and during construction (in accuracy before and during construction (in fabrication and in erectionfabrication and in erection

Features of structural steel construction (cont.)Features of structural steel construction (cont.)Construction aspectsConstruction aspects5.5. Demand greater transportation or Demand greater transportation or cranagescranages

provisionprovision6.6. Complicated quality assurance procedures Complicated quality assurance procedures ––

especially in the control of welding connectionespecially in the control of welding connection7.7. Difficult to make connection with rigid structures Difficult to make connection with rigid structures ––

especially in composite structure in which RC core especially in composite structure in which RC core structure is involvedstructure is involved

8.8. More complex when building become more More complex when building become more gigantic and taller gigantic and taller –– due to the huge number of due to the huge number of structural members, some may be of very heavy structural members, some may be of very heavy section (e.g. those stiffening members)section (e.g. those stiffening members)

9.9. Induce more works at higher altitude Induce more works at higher altitude

Stiffening Stiffening members in the members in the form of outrigger, form of outrigger, belt truss or belt truss or transfer truss is transfer truss is very difficult to very difficult to install during the install during the construction construction processprocess

Outrigger tying up the core Outrigger tying up the core wall and the outer framewall and the outer frame

Detail of the outrigger and Detail of the outrigger and transfer truss system used transfer truss system used in Cheung Kong Centerin Cheung Kong Center

The actual process in The actual process in installing the transfer truss installing the transfer truss ––a temporary support frame a temporary support frame erected for the purposeerected for the purpose

The completion of the The completion of the belt/transfer truss and belt/transfer truss and outrigger at various stagesoutrigger at various stages

Features of structural steel constructionFeatures of structural steel constructionConstruction aspects Construction aspects –– highlight of some highlight of some

problemsproblems Delivery of structural steel member by ship

Large member delivery to site waiting to hoisting up for erection

Features of structural steel constructionFeatures of structural steel constructionConstruction aspectsConstruction aspects

Hoisting of the structural steel member to the upper floor

Features of structural steel constructionFeatures of structural steel constructionConstruction aspectsConstruction aspects

Connecting steel members with RC element – an anchor frame may be required for making strong connection

Features of structural steel constructionFeatures of structural steel constructionConstruction aspectsConstruction aspects

To connect floor to core wall – starter bars are to be provided within the core structure

Constructing the composite floor in steel/RC composite structure

Features of structural steel constructionFeatures of structural steel constructionConstruction aspectsConstruction aspects

Very large component often in complicated shape

Features of structural steel constructionFeatures of structural steel constructionConstruction aspectsConstruction aspects

Huge amount of structural members make erection very complicated

Features of structural steel constructionFeatures of structural steel constructionConstruction aspectsConstruction aspects

The existence of very complicated jointing in steel structure

Features of structural steel constructionFeatures of structural steel constructionConstruction aspects Construction aspects –– highlight of some problemshighlight of some problems

Required to perform works at very high altitude

Features of structural steel constructionFeatures of structural steel constructionConstruction aspectsConstruction aspects

Workers work at high altitude

Features of structural steel constructionFeatures of structural steel constructionConstruction aspectsConstruction aspects

Connecting large and complicate shaped components can be very difficult

Features of structural steel constructionFeatures of structural steel constructionConstruction aspectsConstruction aspects

Examples of location where unmatched dimension causing problem

Concrete has to be trimmed to allow steel to pass through

Features of structural steel constructionFeatures of structural steel constructionConstruction aspectsConstruction aspects

Examples of location where unmatched dimension causing problem

Roof truss and the decking not on the same level

Future development of using structural steel or composite structures in Hong Kong

Instead of building very large and complex building using composite manner, which resulted to very high cost in construction, the following ways may be adopted in order to achieve more cost effective application of technology in future.

1. Use more simple and straight forward design like regular steel frame structure in grid layout

2. Use more standardized components such as universal sections, lattice trusses or prefabricated standard sections in the design

3. Apply more to other types of building structure/construction as in many developed country like Japan, USA, or even Korea and Taiwan

4. Forming hybrid structure with other prefabricated elements

The use of standard structural steel members in construction

Convenient products in market allowing the use of very cheap and effective

ready-install structural steel members to form various building systems

A hybrid structure in Melbourne, Australia with the mixed use ofPrecast concrete, cast-in-situ concrete and steel composite

Detail of the hybrid elements

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