Pendulum Power

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Pendulum Power

The tuned mass damper at Taipei 101 in Taiwan

© Victor Fraile/Corbis

Damping can take many forms. Another solution, especially for skyscrapers, involves suspending an enormous mass near the top of the structure. Steel cables support the mass, while viscous fluid dampers lie between the mass and the building it's trying to protect. When seismic activity causes the building to sway, the pendulum moves in the opposite direction, dissipating the energy.

Engineers refer to such systems as tuned mass dampers because each pendulum is tuned precisely to a structure's natural vibrational frequency. If ground motion causes a building to oscillate at its resonance frequency, the building will vibrate with a large amount of energy and will likely experience damage. The job of a tuned mass damper is to counteract resonance and to minimize the dynamic response of the structure.

Taipei 101, which refers to the number of floors in the 1,667-foot-high (508-meter-high) skyscraper, uses a tuned mass damper to minimize the vibrational effects associated with earthquakes and strong winds. At the heart of the system is a 730-ton (660-metric-ton), gold-colored ball suspended by eight steel cables. It's the largest and heaviest tuned mass damper in the world.

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