A small base isolation system using friction bearings composed of two plates having spherical concave and a ball was developed to prevent overturning small equipment set up inside building during a big earthquake. However it has an amplification problem by resonance. In order to prevent the resonance on this system, the ball of this device is changed to a marble plate or to a ball embedded in a cylindrical sponge. As the results by excitation experiments, the amplification by resonance did not identified, since damping ratio of these systems was increased. The peak acceleration amplitude on these systems has decreased to 42-88 % compared to input waves, and the system using friction bearing with the ball embedded in a cylindrical sponge indicates good reduction in this experiment. And reduction performance of seismic response is evaluated by numerical simulation using SDOF model. Comparing acceleration response waveforms by excitation experiment and by numerical analysis, it was good agreements in case using friction bearing with a ball embedded in a cylindrical sponge. This system is useful for reduction of seismic response.
