SEISMIC BASE ISOLATION OF STEPPED R.C. MULTI-STOREYED BUILDING

Abstract

In this study the effectiveness of base isolation has been studied for stE,ppcd R.C. multi--storeyed buildings of different configurations. . The elastomeric rubber bearings of varied isolation abilities, arc used for stepped R.C. multi-storeyed buildings of different configurations, by interposing these bearings directly under the base of the super ;structure. The elastic structural model for the bearings and the simple plane frame model for the super structure have been adopted for stepped building. Four different earthquake spectra viz. hard rack, medium sail, soft soil and IS Code spectra have been used to simulate the different types of earthquake forces in order to predict the behaviour of such base isolated buildings having different isolation periods. The analysis has been carried out both with conventional fixed base system and base isolated case to determine the essence of base isolation effects of the bearings due to different types of earthquake spectra. A comparison of responses of fixed base case and with base Isolation stopped buildings are carried out for different values of base Isolation periods of the base Isolation systems. The isolation works well In general and the force response decreases with the increase in the flexibility of the bearings in different types of soil spectra. I t is seen that the bearings are very effective for hard rock and for IS Code spectra, for Periods of isolation around 1.0 sac.