Post on 22-Oct-2015
WHAT IS A DIAGRID? The word “diagrid” is a blending of the words “diagonal” and “grid” and refers to a structural system that is single thickness in nature and gains its structural integrity through the use of triangulation. Diagrid systems can be planar, crystalline or take on multiple curvatures. Diagrid structures often use crystalline forms or curvature to increase their stiffness. This differentiates a diagrid from any of the three dimensional triangulated systems such as space frames, space trusses or geodesic structures, although it will be shown that some of the developments of diagrid structures have been derived from the details of these 3‐D systems. The diagrid structural systems that will be explored in this book will focus on the use of diagrid systems in the support of buildings, predominantly examining the perimeter systems that have come to be associated with mid‐rise to tall buildings. These perimeter diagrids normally carry the lateral and gravity loads of the building and are used to support the edge conditions of the floors. Diagrid type systems are also being used as roofs to create large column free clear spans. These types of (predominantly steel) systems have been derived from lamella structures. Where lamella structures may be made from a variety of materials, they predominantly use wood. The majority of lamella structures use a diamond grid and tend not to triangulate. The structural ideas behind the wood lamella contributed to the evolution of the steel lattice grid. Lattice grids are seeing increased use as a structural support system to enable the glazing of large courtyards and enclosed spaces. Lattice grids are designed to span relatively large distances without columns and they typically do not support floor loads. The steel detailing of the lattice grid system is significantly different from that of the perimeter structural diagrid for larger buildings. This type of structure was addressed in my previous book “Understanding Steel Design: An Architectural Design Manual” in the Chapter12: Steel and Glazing Systems. The design and technical exploration of diagrid structures addressed in this book will build on the introductory material addressed in “Understanding Steel Design: An Architectural Design Manual” in Chapter 9: Advanced Framing Systems: Diagrids. THE INTENTIONS OF THIS BOOK Although diagrids have their formative roots in engineering, this book is designed to explore a wide range of questions surrounding their contemporary use in service to architecture. This is not a book with calculations and it is not intended to replace the very necessary collaborative discussions that must take place amongst the architect, engineer and steel fabricator. The text will reference issues of scale and not the absolute size of members. Scale is a very important factor when looking at the relationship between the relative size and exposure of the steel structures to the spaces that they create and define. This would apply to the ultimate impact of diagrid structures on interior spaces as well as urban environments. Diagrid buildings tend to be purposefully selected to function as unique or iconic projects, and the diagrid has been employed to make the building stand out rather than blend into the surrounding urban fabric. FROM SHUKHOV TO FOSTER The origins of the diagrid structural typology lay at the crossroads of engineering and architecture. Engineering first as the initial explorations by Shukhov were intended to provide a structural system that served a civic works function that was not necessarily “architecture” in the purest sense of the word. The initial details and member choices were fairly utilitarian and simple. It is very important that Norman Foster has referenced the work of Shukhov as an inspiration for his diagrid explorations. This affirms the use of Shukhov’s towers as a precedent for buildings such as Swiss Re (30 St. Mary Axe) and the Hearst Magazine Tower. It also allows us to examine the changes that were made to the method of detailing and construction as the hyperbolic paraboloid form transitioned from a “hollow” tower to one that needed to support floor loads and was clad. This is a tremendous change in the role of the structure and the implications on the design, detailing and construction processes undertaken by Foster and ARUP in Swiss Re were significant. The decisions taken in the design of Swiss Re and the Hearst Magazine Tower continue to inform all variations of the diagrid to this date.
DIAGRID STRUCTURES: SYSTEMS, CONNECTIONS, DETAILS Terri Meyer Boake TABLE OF CONTENTS PREFACE 1. A COLLABORATIVE PROCESS
FROM SHUKHOV TO FOSTER
THE INTENTIONS OF THIS BOOK
THE IMPORTANCE OF COLLABORATION
THE ROLE OF BIM
WHY CHOOSE A DIAGRID?
DIAGRID DECISIONS, STEP BY STEP 2. EARLY EVOLUTION OF DIAGRID FRAMING SYSTEMS
BIRTH OF THE DIAGRID IN RUSSIAN CONSTRUCTIVISM
THE IMPACT OF THE MODERN MOVEMENT
GEODESIC DOMES AND SPACEFRAMES
THE EMERGENCE OF THE DIAGONALIZED CORE TYPOLOGY
THE APPEARANCE OF THE DIAGRID SUPPORTED OFFICE BUILDING
THE FORMATION OF THE CONTEMPORARY DIAGRID
A TIME OF STRUCTURAL CHOICE: Diagonalized Cores, Outriggers and Mega Columns 3. THE DEVELOPMENT OF THE CONTEMPORARY DIAGRID
THE CONCEPT AND DEFINITION OF A DIAGRID
EXPLORING THE POSSIBILITIES OF DIAGRID SYSTEMS
STRUCTURAL BENEFITS
THE FIRST CONTEMPORARY DIAGRID BUILDINGS o PROJECT PROFILE: LONDON CITY HALL | FOSTER+PARTNERS, ARUP o PROJECT PROFILE: SWISS RE | FOSTER+PARTNERS, ARUP o PROJECT PROFILE: HEARST TOWER | FOSTER+PARTNERS, WSP CANTOR SEINUK
TIMELINE SHOWING THE PROJECTS IN THIS BOOK 4. TECHNICAL REQUIREMENTS
DESIGNING FOR PERFORMANCE
WIND TESTING
SEISMIC DESIGN
FIRE PROTECTION SYSTEMS o Occupant Safety o Spray Applied Systems o Concrete Filled Tubes o Intumescent Coatings
5. MODULES AND MODULARITY
ISSUES OF SCALE AND SHAPE
GOVERNING STRUCTURAL PERFORMANCE CRITERIA
MODULE SELECTION CRITERIA
OPTIMIZING THE MODULE FOR STRUCTURAL PERFORMANCE OF TALL BUILDINGS
BRACING OF THE DIAGONAL MEMBERS
MODULES AND CORNER CONDITIONS
IMPACT OF THE MODULE ON THE NODE
IMPACT OF THE MODULE ON THE FAÇADE
APPLICATIONS OF MODULES o Small Modules: 2 to 4 Storeys o Mid Size Modules: 6 to 8 Storeys o Large Modues: 10+ Storeys o Irregular Modules
6. NODE AND MEMBER DESIGN
WHAT IS A NODE?
MATERIAL CHOICES
THE BASIS FOR NODE DESIGN: SWISS RE AND HEARST
THE IMPACT OF EXPOSURE ON DESIGN AND DETAILING o Concealed Systems o Architecturally Exposed Systems
NODE ADAPTATIONS FOR CONCEALED SYSTEMS
NODE ADAPTATIONS FOR ARCHITECTURALLY EXPOSED SYSTEMS 7. CORE DESIGN
MATERIAL TRENDS IN TALL BUILDING DESIGN
THE IMPACT OF 9/11 ON CORE DESIGN
THE PURPOSE OF A CORE IN A DIAGRID BUILDING
STEEL FRAMED CORES o Centered Steel Cores o Offset Steel Cores o Steel Cores Outside of the Building o Steel Cores for Hybrid Diagrid Buildings
REINFORCED CONCRETE CORES o Centered Concrete Cores o Concrete Cores for Narrow Plans o Concrete Cores for Highly Eccentric Loading o Concrete Cores for Supertall Buildings
8. CONSTRUCTABILITY
SAFETY ISSUES
ARCHITECTURALLY EXPOSED VERSUS CONCEALED STEEL
ECONOMY THROUGH PREFABRICATION AND REPETITION
IMPACT OF NODE AND MODULE CHOICES ON ERECTION
TRANSPORTATION ISSUES
STAGING AREA AND SITE RELATED ISSUES
MAINTAINING STABILITY DURING ERECTION
9. FAÇADE DESIGN
CLADDING AND FAÇADE TREATMENT
TRIANGULAR GLAZING
RECTILINEAR GLAZING
INTERMEDIARY GLAZING SUPPORT, LATTICE GRIDS 10. EXTERIOR DIAGRIDS
WHEN AN EXTERIOR DIAGRID IS APPROPRIATE
ISSUES WITH EXTERIOR STRUCTURAL DIAGRIDS
DIAGRIDS AS DOUBLE FAÇADE SUPPORT SYSTEMS CONTEMPORARY PROJECTS
TALL BUILDINGS o THE LEADENHALL BUILDING, LONDON, ENGLAND
ROGERS STIRK HARBOUR AND PARTNERS W/ ARUP o CAPITAL GATE, ABU DHABI, UAE
RMJM ARCHITECTS o GUANGZHOU INTERNATIONAL FINANCE CENTER, GUANGZHOU, CHINA
WILKINSON EYRE ARCHITECTS W/ ARUP o ARCELORMITTAL ORBIT TOWER, LONDON, ENGLAND
ANISH KAPOOR, CECIL BALMOND W/ ARUP o DOHA TOWER, DOHA, QATAR
ATELIERS JEAN NOUVEL
UNCONSTRUCTED VISONARY PROJECTS o LOTTE SUPER TOWER, SEOUL, KOREA
SOM o CITIC TOWER, BEIJING, CHINA
TFP ARCHITECTS
DIAGRID TIMELINE A timeline to look at the series of projects that will be addressed in this book in the context of the development of the diagrid, from the early work of Vladimir Shukov, through the diagonalized core typology, to the present. This is by no means a complete list of all of the diagrid buildings constructed to date. The sampling is global and intended to provide a thorough overview of the development of the system.
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BuildingName CompletionDate
BuildingHeightm/ftNo.ofFloors
DiagridType Team
ShukovTowers(various)Russia
Designer:VladimirShukhov
IBMBuilding(UnitedIronworkers)‐Pittsburgh,PA,USA
1963 13floors concealeddiagrid
Architect:CurtisandDavisArchitectsEngineer:LeslieE.RobertsonAssociatesRLLP
JohnHancock‐Chicago,IL,USA
1969 344m/1,128ft/100floors
diagonalizedcore
Architect:SOMEngineer:SOM
BankofChina‐HongKong
1990 367m/1,205ft/72floors
diagonalizedcore
Architect:I.M.PeiEngineer:LeslieE.RobertsonAssociatesRLLP
LondonCityHall‐London,England
2003 10floors diagridtosupportglazing
Architect:Foster+PartnersEngineer:ARUP
SwissRe(St.MaryAxe)‐London,England
2004 180m/590ft/40floors
concealeddiagrid
Architect:Foster+PartnersStructuralengineering:ArupWindsurveyor:RowanWilliamsDavies&IrwinInc.Facadeconsultant:EmmerPfenningerPartnerAGContractor:SkanskaUKSteelsupplier:HollandiaBVandVictorBuyckSteelConstructionNVFacadesupplier:Schmidlin(UK)Ltd.
HearstBuilding‐NewYork,NY,USA
2006 182m/597ft/46floors
concealeddiagrid
Architect:Foster+PartnersEngineer:WSPCantorSeinuk
SeattleCentralLibrary‐Seattle,WA,USA
2005 11floors diagridtosupportglazing
Architect:RemKoolhaas(OMA)Engineer:ARUP
ROM‐Toronto,ON,Canada
2006 6floors concealeddiagrid
Architect:Libeskindw/BregmanandHammanEngineer:ARUP
CantonTower‐Guangzhou,China
2008 600m/1,969ft/ sightseeingtower,externalAESSdiagrid
Architect:MarkHemel/BarbaraKuit/IBAEngineer:ARUP
SIPGTower‐Shanghai,China
2008 37floors diagridfordoublefacade
Architect:EastChinaArchitecturalDesignandResearchInstitute
TornadoTower–Doha,Qatar
2008 195m/640ft/51floors
diagrid Architect:CICOConsultingArchitectsandEngineers,SAITEngineers:StrohandErnstAG
GuangzhouIFC‐Guangzhou,China
2010 439m/1,439ft/103floors
AESSdiagrid
Architect:WilkinsonEyreArchitectsEngineer:ARUP
O‐14‐Dubai,UAE 2010 106m/347ft/24floors
concretediagridvariation
Architects:Reiser+UmemotoEngineer:WSPCantorSeinuk
AldarHQ‐AbuDhabi,UAE
2011 110m/361ft/25floors
concealeddiagrid
Architect:MZAssociatesEngineer:ARUP
CapitalGate‐AbuDhabi,UAE
2011 165m/540ft/36floors
AESSdiagrid
Architect:RMJMArchitectsEngineer:RMJM
KK‐100‐Shenzhen,China
2011 442m/1,499ft/100floors
diagonalizedcore
Architect:TFPEngineer:ARUP
AlBahar‐AbuDhabi,UAE
2012 145m/476ft/29floors
honeycomb Architect:AedasEngineer:ARUP
DohaTower,Qatar 2012 238m/781ft/46floors
AESSdiagrid
Architect:AteliersJeanNouvelEngineer:TerrellGroup,ChinaConstructionDesignInternational
ArcelorMittalOrbitTower‐London,England
2012 diamonddiagrid
Architect:AnishKapoor,CecilBalmondEngineer:ARUP
BowEncana‐Calgary,AB,Canada
2012 237m/779ft/57floors
AESSdiagrid
Architect:Foster+Partnersw/ZeidlerEngineer:Yolles
CCTV‐Beijing,China
2012 234m/768ft/54floors
concealeddiagrid
Architect:RemKoolhaas(OMA)Engineer:ARUP
OneShelleyStreet‐Sydney,Australia
2012 11floors concealeddiagrid
Architect:FitzpatrickandPartnersEngineer:ARUP
CanadianMuseumforHumanRights‐Winnipeg,MN,Canada
2013 concealeddiagrid
Architect:AntoinePredockEngineer:Yolles
ClevelandClinic‐AbuDhabi,UAE
2013 diagridfordoublefacade
Architect:HDRArchitecture
Manukau InstituteofTechnology‐Auckland,NewZealand
2013 5floors AESSdiagrid
Architect:JasmaxArchitects(StephenMiddleton)
LeadenhallBuilding‐London,England
2014 224m/735ft/50floors
AESSdiagrid
Architect:RogersStirkHarbourandPartnersEngineer:ARUP
LotteSuperTower‐Seoul,Korea
2015 555m/1,819ft/123floors
Vision– notbuilt
Architect:SOMEngineer:SOM
ZhongguoZun‐Beijing,China
2016 528m/1,732ft/108floors
Vision– notbuilt
Architect:TFPEngineer:ARUP
STRUCTURE OF THE BOOK
Th e general structure of the book is divided into two parts.
Th e fi rst part of the book is intended to be more instructional and will follow a logical order in terms of its approach to the sequence of topics and type of textual explanations. Images of the full range of projects that I have documented will be included as they are appropriate to the discussion at hand.
Th e second section of the book will be divided into diff erent classifi cations of diagrid applications:
- Tall and Supertall versus mid-rise applications- Curved geometries- Crystalline geometries- Eccentric loading vs. normalized loading- Hybrid diagrid buildings
Th is section will work towards creating a series of more detailed project profi les of each of the subject buildings, including the following documentation:
- Detailed close-up shots of exterior and interior- Photo or drawing of the nodes- Structural axonometric of the building (preferably a Tekla/BIM model)- Construction images (if available)- Descriptions of the way the diagrid system has been incorporated into the design.
INTRODUCTION
Diagrids or diagonal grids are a structural design strategy for constructing large buildings with steel. Th ey create triangular structures with diagonal support beams. Diagrids require less structural steel than a conventional steel frame: Hearst Tower in New York City, designed by Sir Norman Foster, reportedly used 21% less steel than a standard design. Th e Diagrid also obviates the need for large corner columns and provides a better distribution of load in the case of a compromised build-ing.
Diagonalized grid structures have emerged as one of the most innovative and adaptable approaches to structuring build-ings in this millennium. Th e use of diagrids as a formal structural language in buildings started in the early 2000s, exam-ples being Swiss Re, London GLA and Hearst Tower, all from the offi ces of Foster + Partners with ARUP. Today, variations of the diagrid system have evolved to the point of making its use non exclusive to the tall building. Diagrid construction is also to be found in a range of innovative mid-rise steel projects. As a structural type their use is becoming more wide-spread, although information about how to best detail and take advantage of the system is lacking or generalized.
Th e selection a diagrid system is oft en based on architectural choice rather than structural directive,however there are sev-eral functional and economic advantages that underlie the system:- increased stability due to triangulation- diagrids combine the gravity and lateral load bearing systems, thereby providing more effi ciency- provision of alternate load paths in the event of a structural failure- reduced use of structural materials which translates into “carbon” or environmental savings- reduced weight of the superstructure translates into reduced load on the foundations- ability to provide structural support for a myriad of shapes (this has been a reason for the choice of cast concrete for many years as steel tended to be very orthographic)
From the perspective of the project, there are aspects that can be very positive:- the need for a team approach given the complexity of the design and visual impact of the structure on the building design- a high level of cooperation between the architect and engineer- a higher freedom of expression possible given the innate stability of the frame- requirements of expertise and specialization from both architects and engineers
Guangzhou IFC - tallest diagrid building in the world
Capital Gate, UAE - most leaning diagrid in the world
Aldar HQ, UAE - only disk like diagrid building in the world
DEVELOPMENT OF THE DIAGRID
Th is chapter will examine the history of the evolution of diagrid buildings as they evolved through several gen-erations of bracing methods used for tall buildings.
Th e section will include structural issues pertaining to the way that gravity and lateral loads are handled by the diff erent bracing system methods.
How is a diagrid diff erent from a diagonally braced structure?
Short history of changes in methods of diagonal bracing leading up to the invention of the diagrid.
What is a diagrid? Discussion of diagrid terminology (node, module).
Why choose a diagrid? (structural effi ciency, redundancy)
When not to choose a diagrid? (seismic limitations of certain systems, aesthetics, exposure, cost)
John Hancock Tower, Chicago KK100, Shenzhen Bank of China, Hong Kong
THE MODULE
Th is chapter will examine the relationship between the size of the module, height of the building and effi ciency and form.
Th is will build upon current optimization research that is based on numerical studies but include a comparative study of the many projects that will be included in this book to look at how the module infl uences and responds to:
- structural effi ciency- height/width and proportion of the building- choice of fenestration pattern and window size- fl oor to fl oor heights- geometry of the building- eccentric loading- AESS versus concealed steel structures
Hearst Tower, NYC Bow Encana, Calgary Capital Gate, Abu Dhabi
NODE AND MEMBER DESIGN
Th is chapter will examine the design of the members and nodes including material choices and why the majority of diagrids seem to select steel over concrete.
Th e discussion will include:
- the relationship with the module- function of prefabrication- the benefi ts of modularity- dealing with odd shapes and eccentricities as well as many one-of elements- the function of the stiff ness of the node during erection- transportation- selection of the diagrid members- when custom fabrication is required- the impact of the choice to use AESS on the design of these elements
Capital Gate, Abu Dhabi Al Bahar Towers, Abu Dhabi Bow Encana, Calgary
CORE DESIGN
Th is chapter will examine the reasons for choosing steel or concrete for the core based on considerations of:
- constructablity- erection sequencing- local practices or preferences- fi re protection and disaster mitigation issues- structural stability- dimensional characteristics of the building design- impact of and resistance to eccentric loading
Included will be some discussion regarding a change in core design to refl ect terrorism. Regions that might historically have used all steel buildings have more recently changed to composite steel and concrete cores as an anti-terrorism measure.
Freedom Tower, NYC - steel with 3’ of concrete
Swiss Re, London - complete steel frame
Capital Gate - concrete to handle eccentric loading
CONSTRUCTABILITY AND ERECTION ISSUES
Th is chapter will examine the issues surrounding constructing and erecting a diagrid:
- how is constructing a diagrid diff erent from other structural types?- how do choices in node design, member type and length as well as module size impact construction and erec-tion- what are the particular site issues that are unique to diagrid construction- transportation issues associated with nodes and long members- stability during erection (size of member versus temporary shoring)
Some of the issues here will reference back to the design of the core as it is used during the construction process as an answer to some erection issues.
ROM, Toronto - irregular diagrid Hearst, NYC - regular diagrid Orbit Tower, London - modular
THE IMPACT OF EXPOSURE ON DESIGN AND DETAILING ISSUES
Th is chapter will examine the issues surrounding choices to use a concealed or architecturally exposed diagrid.
Whether or not a diagrid is exposed or concealed there will be similar issues from an architectural design per-spective regarding the tendency of the diagrid to dominate the design. Th ere may be instances where the struc-tural system needs to be less visually dominant as a function of the use of the space.
Concealed Structural Steel- detailing of the node- choice of and preferences for members- impact of the module size on the choice of members for concealed steel- fi re protection
Architecturally Exposed Structural Steel- detailing of the node for exposure- choice of and preferences for members- impact of the module size on the choice of members for concealed steel- workmanship issues- fi nishes and fi re protection- scale of exposed systems- when the diagrid dominates the space
Guangzhou IFC - AESS Capital Gate, UAE - AESS London GLA - AESS
CLADDING AND FAÇADE TREATMENT
Th is chapter will examine the envelope related issues.
Th e geometry of the façade will be impacted by: - the size of the module- the planimetric shape of the building- the planar vs sculptural three dimensionality of the building- desire to include natural ventilation- placement of the structural diagrid (inside or outside the envelope)- function of the building (use and partitions)
Triangulated Glazing- when to use- incorporation of natural ventilation
Rectilinear Glazing- when to use- cost issues- incorporation of natural ventilation
Double Façades- how are diagrids used to create double façades- what are the merits(this will be a brief introduction to the topic as it is covered in detail in the next chapter)
Intermediary Structures- use of lattice grids to span or complement diagrid structural systems
Other practical issues such as the window washing and maintance will also be addressed.
SIPG Tower, Shanghai - double façade | triangulated CCTV, Beijing - rectilinear
Guangzhou IFC - super transpar-ent glass
EXTERIOR DIAGRIDS
Th is chapter will examine the choice to place the diagrid on the exterior of the thermal envelope. Th is has been done to support a double facade system or in climates that are temperate and where thermal bridging is not of concern.
Double Façade- structural benefi ts of an external diagrid over a rectilinear system- impact on glazing and ventilation- constructability
Exterior Diagrid Structure- why place on the exterior?- weathering issues- potential structural concerns- potential thermal concerns
Shelley Street, Sydney - ExteriorHospital, Abu Dhabi - Exterior,
double façade O14, Dubai - Exterior concrete
ARCHITECTURAL APPLICATIONS
Th is chapter of the book will be the largest chapter and look to compare diff erent “classifi cations” or “applications” of diagrid structures. Th is will be diff erent than the reference to the projects in Chapters 2 to 9 where the method of diagrid design was explored.
Th e following classifi cations will be used as a method of sorting the projects:
- Tall and Supertall versus mid-rise applications- Curved geometries- Crystalline geometries- Eccentric loading vs. normalized loading- Hybrid diagrid buildings
Th is section will work towards creating a series of more detailed project profi les of each of the subject buildings, including the following documentation:
- Detailed close-up shots of exterior and interior- Photo or drawing of the nodes- Structural axonometric of the building (preferably a Tekla/BIM model)- Construction images (if available)- Descriptions of the way the diagrid system has been incorporated into the design.
Th e level to which the project profi les can be consistently developed will be a function of the ability to source additional materials from the architects, engineers and fabricators. It is the intention of the Project Profi les to use as much “ready made” material that would have formed a part of the design and construction process. It is not my intention to commission new drawings.
Aldar HQ, Abu Dhabi Guangzhou IFC Hotel Atrium Hearst Tower Atrium
CURRENT STATE OF DIAGRID RESEARCH
Th is chapter will summarize the fi ndings of the book and speak to what is being done in current research includ-ing mention of projects that are presently either “on the boards” or in the early stages of construction.
Most of the published research is highly numeric and directed at University engineering research. It is my sense that much of the “real research” is being done in the engineering and architectural offi ces associated with these projects. Where academia is looking for optimization, practice seems geared towards innovation and the break-ing of records.
Canadian Museum for Human Rights, Winnipeg Al Bahar Towers, Abu Dhabi Diagrid building, Auckland