Pendulum Device To Reduce Swaying Of Skyscrapers During Quakes

Pendulum device to reduce swaying of skyscrapers during quakesTwo companies have developed a seismic control device weighing several hundred tons that can be installed on top of skyscrapers to suppress slow and large vibrations on the upper floors during major earthquakes.

Real estate developer Mitsui Fudosan Co. and general contractor Kajima Corp. said July 29 that the device uses giant steel pendulums hung on the rooftop level that will apply force in the direction opposite of “long-period seismic motions,” thereby more than halving the amplitude of vibrations.

The companies said they will spend about 5 billion yen ($51 million) to install the first device on top of Shinjuku Mitsui Building, a 55-story skyscraper in Tokyo, in 2015. The device will comprise six pendulums, each weighing 300 tons, to suppress swaying during earthquakes.

Shinjuku Mitsui Building experienced horizontal vibrations of about 2 meters during the magnitude-9.0 Great East Japan Earthquake on March 11, 2011. Such motions can damage building interiors and injure people inside.

The new device can not only reduce the vibrations by about 60 percent but could also shorten their duration during a potential earthquake of a similar scale, the companies said.

New high-rise buildings are often built with the pendulum technology. The device can be installed on the top of older skyscrapers without having to take up space inside.