ARUP

China Central Television (CCTV) Headquarters building at the heart of Beijing’s Central Business District is a 234 metre-tall, three-dimensional ‘cranked loop’. The building is formed by two leaning towers, bent 90° at the top and bottom to meet in an overhang and counterweight base.

The highly unusual shape means that by its nature the CCTV Headquarters has some very complicated twisting and overturning characteristics.  Enabling the tower to defy the laws of gravity proved an unparalleled engineering challenge, not least because the building needs to withstand a high level of seismic activity.

The CCTV Headquarters base acts as a ‘heel’, ensuring that gravity and wind loads are evenly distributed into the ground.  Support is achieved through the irregular grid on the building’s surface – a visible expression of the forces travelling through the tube structure. The smaller the diagonal pattern, the stronger the load and the greater the support given.

Specially designed computer programmes simulated how the building would respond millisecond by millisecond to earthquakes of various intensities.  The supporting grid was ‘tuned’ to find the balance between making the building strong enough for everyday conditions in Beijing, yet flexible enough to withstand a major earthquake.

Before the two towers were linked they were prone to independent movement from wind and surface temperature variations due to direct sunlight.  The towers were joined in mid-December 2007 at nine o’clock in the morning, on a windless day when the temperature of the tube structures had the least variation due to direct sunlight.  Had the towers been joined at noon on a summer day, the heat would have caused the steel in some of the buildings surfaces to expand slightly, skewing the structure out of alignment.

Arup also performed security consulting for the CCTV Headquarters.