CCTV Building, A Structural Design Overview

The CCTV building is one of the several big Beijing Olympic projects, which houses the headquarters for the Chinese Central Television Network. Its design shows unique style, but great structural engineering challenges to overcome. The following presentation provides an overview of how these challenges were overcome. (Presented at Monash University, Department of Civil Engineering, August 2008).

1. CCTV Headquarters, Beijing A Structural Design Overview By Peter M. Bach (August, 2008)

2. Before we start… Will it stand by itself?

3. Before we start… It can! But the question is: How much effort does it take to make it fall?

4. Before we start… THIS?!

5. Topics General Project Details Architecture Construction Challenges Diagrid Framing System Other Structural Features Miscellaneous Topics The Other Buildings Conclusion

6. General Project Details

7. 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

8. General Project Details Location In Beijing’s CBD (Third Ring Road) East of Forbidden City

9. General Project Details Admin – Site – History Project Manager: Dongmei Yao Partners in Charge: Ole Sheeren & Rem Koolhaas Architects: 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

10. 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)

11. General Project Details Admin – Site – History (cont.) Towers Lean at 60 o 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

12. General Project Details Space Usage

13. General Project Details Space Usage (cont.) Yellow = Canteens Dark Blue = Studios Green = Open Studios Orange = Lobbies (Tower & Sky) Pale Green = Broadcasting Light Blue = Sports & Recreation Red = 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

14. 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”

15. Architecture

16. Architecture What do you think “logic” and “beauty” is defined as?

17. Architecture The Skyscraper Concept What do all the above buildings have in common? Height! Human Capabilities

18. Architecture The CCTV’s Concept Architect: Rem Koolhaas China willing to try out new ideas Everything 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

19. Architecture The Architect’s Opinion Community combined as opposed to separate Concentrate 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

20. Architecture The Basic Geometry Mobius Strip (continuous loop) Cantilever Overhang Diagonal Structural Grid System L-Shaped

21. Construction Challenges

22. 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 loads Temperature changes, material deformation Subsoil Conditions: Shallow foundation not sufficient Pore Water present in great amounts High Settlement Risk

23. Construction Challenges What kinds of Challenges will this Project face? Needs to accommodate 10,000 people, heavy equipment  High service loads Vulnerable to Natural or Man-Made Disasters How to design & construct? Performance-based Design Approach

24. Diagrid Framing System

25. 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

26. 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

27. Diagrid Framing System Load Transfer 1.) Vertical Loads 2.) Lateral Loads

28. Diagrid Framing System Load Transfer Load 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

29. Diagrid Framing System Advantages of this System Structurally 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

30. 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)

31. Diagrid Framing System Disadvantages of this System Not 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

32. Other Structural Features

33. Other Structural Features Connections – Butterfly Plates Critical 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

34. Other Structural Features Connections – Butterfly Plates

35. 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

36. Other Structural Features Load Transfer Assistance - Trusses Hidden 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

37. Other Structural Features Load Transfer Assistance - Trusses

38. 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)

39. Miscellaneous Topics

40. Miscellaneous Topics Construction Procedure

41. Miscellaneous Topics Seismic Stability Design Approach CCTV 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

42. Miscellaneous Topics Seismic Stability Design Approach Other 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

43. Miscellaneous Topics Dealing with Wind Wind 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

44. Miscellaneous Topics Emergency Scenarios In 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?

45. Miscellaneous Topics Emergency Scenarios (cont.) Numerous Escape Routes Looped Structure an Advantage Reduced Escape Time Better Safety

46. The Other Buildings

47. The Other Buildings The TVCC Building Hotels, Theaters, Cultural Center for Performing Arts

48. The Other Buildings Service Building & Media Park Service Building: Energy Center, Guards Dormitories, Major Broadcasting Vehicle Garages, Fire Control Center Media Park: Social Gathering place, filming options

49. Construction Progress Latest Pictures of the Building Dated June 2008

50. Conclusion

51. 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

52. 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 25 th 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 25 th May 2008 [6] Koolhaas, R., (2004), “Beijing Manifesto”, Wired Issue 8 2004 [7] Lee, S., “Nonlinear Dynamic Earthquake Analysis of Skyscrapers”, CTBUH 8 th 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 25 th May 2008 [9] “OMA – New Head Quarters – Central Chinese Television”, arcSpace.com, http://www.arcspace.com/architects/koolhaas/chinese_television/ , Last Accessed 25 th 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 25 th 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 25 th 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

53. Questions