Abstract

Seismic base isolation systems have been investigated in this study to be acquainted with the optimized insertion in multi-storey buildings. Two extensively exploited isolator types, namely, lead rubber bearing (LRB) and high damping rubber bearing (HDRB) are incorporated to examine their effect for buildings. Both time history and response spectrum based non linear finite element analyses are conducted using SAP 2000 program as analysis tool. Isolators are designed as per UBC code. Bi- directional site specific earthquake records have been used as seismic load. Analyses results show that isolation system considerably reduce earthquake induced load on building. Furthermore, method of analysis has been found to have considerable effect on the response of low to medium rise buildings. Time history analysis shows significant less base shear than that from response spectrum analysis. Also, less isolator displacement is obtained from time history analysis than that from response spectrum analysis. Considering isolator displacement and base shear, HDRB is found to be better of the two types of isolators adopted in this study. Nevertheless, LRB is stumbled on to be more effectual in reducing individual floor acceleration and thereby reducing non structural damages.

Key words: Optimal isolation system, response spectrum analysis, time history analysis, lead rubber bearing (LRB), high damping rubber bearing (HDRB), bi-directional earthquake, low to medium rise buildings, flexibility, seismic resistance.