Recently, in Japan, a growing interest has arisen in the development and securing of the amenities required for living spaces. The reduction of the uncomfortable sway motion of high-rise buildings, induced by comparatively strong winds, is a subject of central importance in this area.
The authors have been able to develop a motion reduction device equipped with new mechanism. This device is actually a tuned active damper (TAD), which is equipped with both a tuned spring system and a control system. It is able to act in dual directions. The tuned spring system has a multi-stepped pendulum with a period of 6.0 sec. and an AC servomotor is used for the control system. Two devices of this type are installed on the first floor of the penthouse of the MM 21 Landmark Tower.
The height of the tower is 296m and the location of the installation of the devices is at 282m. The devices are small and have an effective weight ratio of 0.6%. The criterion for habitability has been fixed at 5.8 cm/sec2 (rms value) for the response acceleration at the top of the building in light of the ISO 6897. This criterion is set up for a wind force with a return period of five years. The installation of the tuned active dampers can reduce the building's degree of swaying motion by more than 12, which effectively satisfies the criterion.
These devices were designed with thorough consideration given to safety. This has indeed been confirmed through the use of a test employing a 14 scale model.