Download - CCTV Building, A Structural Design Overview
CCTV Headquarters, Beijing
A Structural Design OverviewBy Peter M. Bach (August, 2008)
Before we start…
Will it stand by itself?
Before we start…
It can! But the question is: How much effort does it take to make it
fall?
Before we start…
THIS?!
Topics
General Project DetailsArchitectureConstruction ChallengesDiagrid Framing SystemOther Structural FeaturesMiscellaneous TopicsThe Other BuildingsConclusion
General Project Details
General Project Details
Background The new HQ for China’s CCTV
Completion in time for Olympics
Will broadcast the Olympics to the World
Components:CCTV Building (Headquarters & Broadcasting)TVCC Wing (Cultural Center, Performing Arts)Media Park (Social Gathering Place)
First of 300 towers to be constructed in Beijing’s CBD
General Project Details
LocationIn Beijing’s CBD (Third Ring Road)East of Forbidden City
General Project Details
Admin – Site – History Project Manager: Dongmei YaoPartners in Charge: Ole Sheeren & Rem KoolhaasArchitects: Office for Metropolitan Architecture (OMA)Structural Engineers: Ove Arup & Partners
10-hectare site
Two L-Shaped Towers, tallest tower is 230m high
Total Estimated Construction Cost: €600million
Will employ 10,000 people
General Project Details
Admin – Site – History (cont.)
Comparing Building Heights in Asia
Comparing Building Heights in the World
“…The building is by any conventional definition a Skyscraper…”
(UK Telegraph)
General Project Details
Admin – Site – History (cont.) Towers Lean at 60o angles and “kink” at right angles at the top
Cantilever overhang starts after 36 floors and is 13 floors high.
The towers cantilever 75m outwards
History December 2002 - OMA wins design March 2003 – Project Start (after review) September 2004 – Groundbreaking Mid 2007 – Overhang Construction Underway Early 2008 – Finalizing Construction
General Project Details
Space Usage
Administration16.13%
Program Of-fices
13.98%
News Pro-duction15.05%Broadcasting
8.60%
Program Production
25.81%
Staff Facilities6.45%
Parking13.98%
CCTV Total Area Distribution
Administration
Program Offices
News Production
Broadcasting
Program Production
Staff Facilities
Parking
General Project Details
Space Usage (cont.)Yellow = CanteensDark Blue = StudiosGreen = Open StudiosOrange = Lobbies (Tower & Sky)Pale Green = BroadcastingLight Blue = Sports & RecreationRed = VIP Areas
- Lobbies on Ground & Top Floors
- Recreation mainly on bottom
- Elevators in both towers
- Separate Lobby & Elevator for
VIPs
- Two Ground Floor Lobbies
- Continuous Loop through
Towers
- Studios mainly on the lower
Floors
General Project Details
Nicknames & Descriptions
“Twisted Donut”
“The Pants”
“Two drunken, upside-down Ls”
“Each Tower is a banana, built with a deliberate slight curve…”
“Contorted Loop”
“Lopsided Colossus”
Architecture
Architecture
What do you think “logic” and “beauty” is defined as?
Architecture
The Skyscraper Concept
What do all the above buildings have in common?
Height! Human Capabilities
Architecture
The CCTV’s ConceptArchitect: Rem KoolhaasChina willing to try out new ideasEverything to do with TV Production is within the CCTV Building (“An inter-connected loop of inter-connected activities”)Iconographic Constellation instead of hopeless race for ultimate height“…As verticality soars, creativity crashes…”“…An Expression of Verticality…”Idea should create buildings that will actively engage the cityscape
Architecture
The Architect’s OpinionCommunity combined as opposed to separateConcentrate every program into a single system“It is important to encourage different kind of work of
engineering as it is with architecture”“Experimenting with Engineering liberates imagination
and makes other things possible”
The idea links a bit with communism as is still seen in China
“There is a natural affinity between the values of architecture and the values of socialism”
Hopes to spread this new building idea in Europe
Architecture
The Basic GeometryMobius Strip (continuous loop)Cantilever OverhangDiagonal Structural Grid SystemL-Shaped
Construction Challenges
Construction Challenges
What kinds of Challenges will this Project face?
A lot steel is used Weight Issues (instability)Beijing is an Earthquake Prone Area (need seismic stability)Every building encounters vertical and lateral loadsTemperature changes, material deformationSubsoil Conditions:
Shallow foundation not sufficientPore Water present in great amountsHigh Settlement Risk
Construction Challenges
What kinds of Challenges will this Project face?Needs to accommodate 10,000 people, heavy equipment High service loadsVulnerable to Natural or Man-Made DisastersHow to design & construct?
Performance-based Design Approach
Diagrid Framing System
Diagrid Framing System
What is it? Short for Diagonal Grid System
Triangulated structure with diagonal support beams
Similar to a typical moment frame
Triangles connected at Nodes and Rings intersect the nodes
Combines the benefits of a hollow tube with a truss
Loads follow diagonals, gravity and lateral loads can be transferred by the system to the ground
Swiss Re, London
Diagrid Framing System
What is it? (cont.)Can be constructed of either:
Steel (most common) Timber Reinforced Concrete
Steel is typical because of high tensile and compressive strengths
Essentially marrying columns, diagonals and bracings into one system
Not a new technology, used in early aviation and small-scale structures
Diagrid Framing System
Load Transfer
1.) Vertical Loads
2.) Lateral Loads
Diagrid Framing System
Load TransferLoad transfer happens primarily through diagrid
Internal Cores will transfer minimal amounts of gravity loads Floor Slabs do not have to transfer lateral loads Less internal columns required = more space Floor plates do not have to be of the same shape on each
floor
Continuous and Uninterrupted Load Transfer
Rings help to resist Buckling Loads transforming whole system into one big tube
Diagrid Framing System
Advantages of this SystemStructurally very strong
Less material required (~20% reduction in steel as opposed to typical moment frame method)
Aesthetically Pleasing – Blends in together with façade
Floor plan becomes open and free – more internal space
Most forms can be created with a triangulated form – architectural freedom
Self-reliant structure, simple in shape
Diagrid Framing System
Advantages of this System (cont.)Simple Construction Technique
Skyscraper Structural Failure minimized by diagrid construction
Better ability to redistribute loads than a moment frame (Failure of one portion does not mean complete structural failure)
Diagrid Framing System
Disadvantages of this SystemNot thoroughly explored for skyscraper construction yet
Inexperienced construction crews
A diagrid structure will definitely show in the aesthetics, very difficult to hide
Difficult to create a consistent window design
Heavy-handed if not executed properly
Material usage can be very excessive if loads are not high
Other Structural Features
Other Structural Features
Connections – Butterfly PlatesCritical Members in the Structural System
Must ensure a “strong joint-weak member” system
Must resist maximum probable load from braces with minimum yielding and stress concentration
Butterfly plates used to assist smooth load transfer
Finite Element Analysis of Connection
Other Structural Features
Connections – Butterfly Plates
Other Structural Features
Foundation – Piled Raft Total Settlement estimated as <100mm
Differential Settlement kept to 1:500
Piles are 1.2m diameter and 35m long
Piled Raft is 7m thick and has a footprint greater than the towers
Tension piles used away from towers to resist uplift pressures
Other Structural Features
Load Transfer Assistance - TrussesHidden from view for architectural purposes inside
Link up external columns with internal steel core via pin-joints
Trusses span the bottom two floors of the overhang, loads above are transferred to these trusses, which subsequently transfer loads to the diagrid system
Major trusses located at building base (podium) to support the above loads
Other Structural Features
Load Transfer Assistance - Trusses
Other Structural Features
Building Internal Cores
Three main cores accommodating elevators
Cores remain vertical despite Tower Slope (shifted against floor plates)
One core dedicated to “Grandness” (Administrative), the other to “Newness” (News & Technology)
Miscellaneous Topics
Miscellaneous Topics
Construction Procedure
Miscellaneous Topics
Seismic Stability Design ApproachCCTV Performance-based Design for Seismic Stability well outside National Building Codes
Analysis for different seismic events
Level 1: Frequent Earthquake No structural damage
Level 2: Intermediate Earthquake Repairable Structural Damage
Level 3: Rare Earthquake Severe Structural Damage permitted, must not collapse
Miscellaneous Topics
Seismic Stability Design ApproachOther Research shows test results depicting Overhang vertical displacement with time during an Earthquake
Tests also show that some braces go into plastic buckling during the Earthquake Dissipate seismic energy (GOOD)
Maximum downward displacement = 700mm
Miscellaneous Topics
Dealing with WindWind Tunnel Experiments had to be carried out to assess the severity of Wind Loads
Building strength against a 100-year Wind was assessed
Method: Dynamic Analysis using High-Frequency Pressure Integration Method
285 Pressure Taps installed on 1:500 Scale Model
North and West Winds Critical
Southwest Wind worst for Vertical Loads
Miscellaneous Topics
Emergency ScenariosIn the event of a fire or a major disaster (natural or man-made) that causes major structural damage, what are the possible escape routes and how long will it take?
Miscellaneous Topics
Emergency Scenarios (cont.)Numerous Escape Routes
Looped Structure an Advantage
Reduced Escape Time
Better Safety
The Other Buildings
The Other Buildings
The TVCC BuildingHotels, Theaters, Cultural Center for Performing Arts
The Other Buildings
Service Building & Media ParkService Building: Energy Center, Guards Dormitories, Major Broadcasting Vehicle Garages, Fire Control Center
Media Park: Social Gathering place, filming options
Construction Progress
Latest Pictures of the Building
Dated June 2008
Conclusion
Conclusion
Building is to become an icon of Beijing’s Cityscape once completed and will play an important role for the 2008 Olympics
Architecture looks at iconography rather than the race for height – engineering creativity is better than height
Many structural challenges to overcome in realizing the project Performance-based design needed
Diagrid System, Butterfly Plates, Piled Raft Foundations, Load Transfer Trusses all deemed good solutions
Seismic and Wind Stability ensured through rigorous analysis
Emergency Escape Routes are effective
Other buildings on-site serve unique functions
References[1] Carroll, C., Xiaonian, D., Gibbons, C., Lawson, R., Lee, A., Luong, A., Megowan, R., Pope, C., (2006), “China Central Television Headquarters – Structural Design”, Steel Structures 6
[2] CB Richard Ellis, (2007), “The CCTV Tower: Central Icon of Post-Urban Beijing?”, CBRE Research – Asia 2007 Issue 1
[3] “CCTV Address”, China Academic Journal Electronic Publishing House, http://www.ckni.net, Last Accessed 25th May 2008
[4] “CCTV by OMA”, A+U Architecture & Urbanism July 2005 Special Issue, Tokyo, Japan
[5] “China Central Television (CCTV) Headquarters”, Design Build Network, http://www.designbuild-network.com/projects/cctv/, Last Accessed 25th May 2008
[6] Koolhaas, R., (2004), “Beijing Manifesto”, Wired Issue 8 2004
[7] Lee, S., “Nonlinear Dynamic Earthquake Analysis of Skyscrapers”, CTBUH 8th World Congress, Dubai 3-5 March 2008
[8] McCain, I., “DiaGrid: Structural Efficiency & Increasing Popularity”, http:// daapspace4.daap.uc.edu/~larsongr/Larsonline/SkyCaseStu_files/Diagrid.pdf, Last accessed 25th May 2008
[9] “OMA – New Head Quarters – Central Chinese Television”, arcSpace.com, http://www.arcspace.com/architects/koolhaas/chinese_television/, Last Accessed 25th May 2008
[10] Telegraph.co.uk, “2008 Olympics: New Towers for a New Superpower”, UK Telegraph, http://www.telegraph.co.uk/arts/main.jhtml?xml=/arts/2007/12/29/babeijing129.xml, Last Accessed 25th May 2008
[11] Telegraph.co.uk, “China’s ambitious building passes key test”, UK Telegraph, http://www.telegraph.co.uk/news/uknews/1572347/China%27s-ambitious-building-passes-key-test.html, Last Accessed 25th May 2008
[12] Xie, J. , To, A., “Design-Oriented Wind Engineering Studies New China Central Television Headquarters”, Technotes Issue No. 26, RWDI Consulting Engineers & Scientists
Questions