The 728-Ton Tuned Mass Damper of Taipei 101

Taipei 101 is an iconic skyscraper located in the city of Taipei, in Taiwan. It rises to 509 meters and consist of exactly 101 floors. At the time of its construction in 2004, it was the tallest building in the world – a title it held on to until the Burj Khalifa came into being in 2010.
Sitting just 660 ft. from a major fault line, Taipei 101 is prone to earthquakes and fierce winds common in its area of the Asia-Pacific. The engineers had to design a structure that could withstand gale winds up to 216 km/h and the strongest earthquakes. Typically skyscraper must be flexible in strong winds yet remain rigid enough to prevent large sideways movement. Flexibility prevents structural damage while resistance ensures comfort for the occupants and protection of glass, curtain walls and other features. Most designs achieve the necessary strength by enlarging critical structural elements such as bracing, but the height of Taipei 101 combined with the demands of its environment called for additional innovations.
taipei-101-damper-6

Photo credit
To achieve stability and lessen the impact of violent motion, a gigantic tuned mass damper was designed. The damper consist of a steel sphere 18 feet across and weighing 728 ton, suspended from the 92nd to the 87th floor. Acting like a giant pendulum, the massive steel ball sways to counteract the building’s movement caused by strong gusts of wind. Eight steel cables form a sling to support the ball, while eight viscous dampers act like shock absorbers when the sphere shifts. The ball can move 5 ft. in any direction and reduce sways by 40 percent. Two additional tuned mass dampers, each weighing 7 tons, installed at the tip of the spire provide additional protection against strong wind loads.
The engineers were so proud of their creation that they made the damper publicly visible from an indoor observatory located inside the tower, where recorded voice tours and informative displays explain to visitors how the thing works. During particularly windy days one can see the damper in action. The following video was recorded by a tourist during the 2008 Sichuan earthquake.
Taipei 101’s damper was built at a cost of US$4 million, and it is the world’s largest tuned mass damper, and perhaps the only one visible to the public.
Taipei_101_Damper