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?!

6. Architecture

7. Construction Challenges

8. Diagrid Framing System

9. Other Structural Features

10. Miscellaneous Topics

11. The Other Buildings

14. Completion in time for Olympics

15. Will broadcast the Olympics to the World

16. Components:

17. CCTV Building (Headquarters & Broadcasting)

18. TVCC Wing (Cultural Center, Performing Arts)

19. Media Park (Social Gathering Place)

22. Partners in Charge: Ole Sheeren & Rem Koolhaas

23. Architects: Office for Metropolitan Architecture (OMA)

24. Structural Engineers: Ove Arup & Partners

25. 10-hectare site

26. Two L-Shaped Towers, tallest tower is 230m high

27. Total Estimated Construction Cost: €600million

30. Cantilever overhang starts after 36 floors and is 13 floors high.

31. The towers cantilever 75m outwards

32. History

33. December 2002 - OMA wins design

34. March 2003 – Project Start (after review)

35. September 2004 – Groundbreaking

36. Mid 2007 – Overhang Construction Underway

39. Recreation mainly on bottom

40. Elevators in both towers

41. Separate Lobby & Elevator for VIPs

42. Two Ground Floor Lobbies

43. Continuous Loop through Towers

45. Architecture

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

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

49. China willing to try out new ideas

50. Everything to do with TV Production is within the CCTV Building (“An inter-connected loop of inter-connected activities”)

51. Iconographic Constellation instead of hopeless race for ultimate height

52. “…As verticality soars, creativity crashes…”

53. “…An Expression of Verticality…”

55. Concentrate every program into a single system

56. “It is important to encourage different kind of work of engineering as it is with architecture”

57. “Experimenting with Engineering liberates imagination and makes other things possible”

58. The idea links a bit with communism as is still seen in China

59. “There is a natural affinity between the values of architecture and the values of socialism”

61. Cantilever Overhang

62. Diagonal Structural Grid System

65. Beijing is an Earthquake Prone Area (need seismic stability)

66. Every building encounters vertical and lateral loads

67. Temperature changes, material deformation

68. Subsoil Conditions:

69. Shallow foundation not sufficient

70. Pore Water present in great amounts

72. Vulnerable to Natural or Man-Made Disasters

73. How to design & construct?Performance-based Design Approach

74. Diagrid Framing System

76. Triangulated structure with diagonal support beams

77. Similar to a typical moment frame

78. Triangles connected at Nodes and Rings intersect the nodes

79. Combines the benefits of a hollow tube with a truss

80. Loads follow diagonals, gravity and lateral loads can be transferred by the system to the groundSwiss Re, London

82. Steel (most common)

83. Timber

84. Reinforced Concrete

85. Steel is typical because of high tensile and compressive strengths

86. Essentially marrying columns, diagonals and bracings into one system

89. Internal Cores will transfer minimal amounts of gravity loads

90. Floor Slabs do not have to transfer lateral loads

91. Less internal columns required = more space

92. Floor plates do not have to be of the same shape on each floor

93. Continuous and Uninterrupted Load Transfer

95. Less material required (~20% reduction in steel as opposed to typical moment frame method)

96. Aesthetically Pleasing – Blends in together with façade

97. Floor plan becomes open and free – more internal space

98. Most forms can be created with a triangulated form – architectural freedom

100. Skyscraper Structural Failure minimized by diagrid construction

102. Inexperienced construction crews

103. A diagrid structure will definitely show in the aesthetics, very difficult to hide

104. Difficult to create a consistent window design

105. Heavy-handed if not executed properly

108. Must ensure a “strong joint-weak member” system

109. Must resist maximum probable load from braces with minimum yielding and stress concentration

110. Butterfly plates used to assist smooth load transfer

113. Differential Settlement kept to 1:500

114. Piles are 1.2m diameter and 35m long

115. Piled Raft is 7m thick and has a footprint greater than the towers

117. Link up external columns with internal steel core via pin-joints

118. Trusses span the bottom two floors of the overhang, loads above are transferred to these trusses, which subsequently transfer loads to the diagrid system

121. Cores remain vertical despite Tower Slope (shifted against floor plates)

123. Miscellaneous Topics Construction Procedure

125. Analysis for different seismic events

126. Level 1: Frequent Earthquake  No structural damage

127. Level 2: Intermediate Earthquake  Repairable Structural Damage

129. Tests also show that some braces go into plastic buckling during the Earthquake  Dissipate seismic energy (GOOD)Maximum downward displacement = 700mm

131. Building strength against a 100-year Wind was assessed

132. Method: Dynamic Analysis using High-Frequency Pressure Integration Method

133. 285 Pressure Taps installed on 1:500 Scale Model

134. North and West Winds Critical

136. Looped Structure an Advantage

137. Reduced Escape Time

141. Conclusion

143. Architecture looks at iconography rather than the race for height – engineering creativity is better than height

144. Many structural challenges to overcome in realizing the project  Performance-based design needed

145. Diagrid System, Butterfly Plates, Piled Raft Foundations, Load Transfer Trusses all deemed good solutions

146. Seismic and Wind Stability ensured through rigorous analysis

147. Emergency Escape Routes are effective

149. Questions