Abstract
For reduction of seismic response, many types of base isolation systems are developed. Friction mechanism is utilized in some of them. In general, responses decrease with the increase of friction coefficient. However, acceleration responses increase at a friction coefficient in some conditions of experiments. In order to examine the phenomenon using random vibration theory, mean square responses of the system with friction are calculated using equivalent linearization method. Seismic excitations are simulated as nonstationary filtered white noise. The maximum acceleration and displacement responses are obtained. In some conditions, the optimal friction coefficient exists. The optimal coefficient gives the minimum acceleration response. Isolation systems are not effective for small excitations because responses are not reduced.
