Abstract
For the purpose of reducing seimic responses of structures, an earthquake isolation equipment using mechanism of lever and pendulum installed to the structures have been developed. Theoretical analysis shows that the earthquake isolation equipment has the same dynamic properties as a dynamic absober usually used for isolating mechanical vibration. The natural frequency of structure is divided to two frequencies by installing an appropriate designed earthquake isolation equiment. As spectra of earthquake ground motions are generally wide band, performance of earthquake isolation equipment depends on the damping properties used in the structure and equiment. Therefore, the authors have studied the damping effect on the seismic responses under the consideration of the experimental results of damping properties. From this, it is found that the proper amount of damping reduces seismic responses of the structure. By the statistcal analysis of time integration computations of responses of the structure with earthquake isolation equipment to 11 earthquake ground motions, it is found that optimally designed earthquake isolation equiment with optimal amount of damping can reduce base shear transmitting to a foundation (Q_B) to 0.6〜0.7 of base shear without equiment (Q_0), i.e. Q_<Bmax>/Q_<0max>=0.6〜0.7. Horizontal force Q_<1max> can also be reduced to 0.6〜0.7 of Q_<0max>, i.e. Q_<1max>/Q_<0max>=0.6〜0.7. From the above theoretical analyses, it is found that the earthquake isolation equipment using mechanism of lever and pendulum is useful for reducing seismic responses of structures.
