Seismic isolation of a floor

Fig. 14-10: A translational suspended floor (Courtsy of Porf. M Kawaguchi)

As the natural frequency of a translational suspended system is only governed by its length and is independent of its mass, the concept of a pendulum seismic isolator was developed and used in Japan.

As shown in Fig. 14-10, a floor suspended from girders of a building frame in the form of a translational suspended system was adopted for the exhibition rooms of an actual museum for pottery and porcelain in Japan. The area of the suspended floor is about 1000 , and its mass is about 1000 tonnes. Hinges having universal joints were used for the upper and lower ends of the hangers. The hangers were 4.5 m long, producing a natural period of more than 4 seconds, which was considered sufficiently long for seismic isolation.