Design of sliding-type base isolators by the concept of equivalent damping

One problem with base isolators of the sliding type is that their dynamic r esponses are nonlinear, which cannot be solved in an easy manner, as distin ction must be made between the sliding and non-sliding phases. The lack of a simple method for analyzing structures installed with base isolators is o ne of the obstacles encountered in application of these devices. As an init ial effort toward simplification of the analysis procedure for base-isolate d structures, an approach will be proposed in this paper for computing the equivalent damping for the resilient-friction base isolators (R-FBI), based on the condition that the sum of the least squares of errors of the linear ized response with reference to the original nonlinear one is a minimum. Wi th the aid of equivalent damping, the original nonlinear system can be repl aced by a linear one, which can then be solved by methods readily available . in this paper, equivalent damping curves are established for all ranges o f the parameters that characterize the R-FBI for some design spectra.