The Performance-Based Earthquake-resistant Evaluation Method Of Rubber Bearing Base Isolation

In recent years, performance-based earthquake-resistant design theory is more and more attached importance, and this method has its advantage when it is applied to design of structure-controlled system. Spectrum method is a elastic -plastic analysis and easy to use. It not only avoids the troubles of Time History analysis, but also does the Elastic-plastic analysis for the structure in earthquake. This paper applies the spectrum method evaluates the seismic performance of Rubber Bearing Base isolation.According to characteristics of the base-isolated structures, this paper adopts three performance levels to evaluate the seismic performance of base-Isolated structures. This paper applies the capacity spectrum method to evaluate the base isolated structures' performance, and analyzes the questions of mechanical model, distributions of the lateral forces, establishment of demand spectrum and evaluated indexes.Based on the basic principle of capacity spectrum method and certain hypothesis, the one degree freedom equivalent method for structures with the rubber bearing base-isolation system is put forward. According to the hysteretic characteristic of rubber bearing, calculation method of equivalent damping for structure with the rubber bearing base-isolation system is proposed and elastic-plastic response spectra of this system is obtained on the foundation of discounting elastic spectra of seismic design code for buildings using equivalent damping. A pushover analysis of 8 floor frame structure with support of rubber vibration isolation cushion is given by SAP2000 finite element software and it at last indicates the suggested formula of distribution pattern of lateral force is in accord with time history analysis method and the new formula has high reliability. Performance evaluation of capacity spectrum method and time-history analysis of the structure are at the same time given, the result shows that evaluation based on capacity spectrum method of structure with base-isolation system has certain reliability. The result of time history analysis presents that structure with base-isolation system could effectively reduce seismic response under common and seldom earthquake actions.