SEISMIC ANALYSIS OF LOW TO MEDIUM RISE BUILDING FOR BASE ISOLATION

H.P. Santhosh, K.S. Manjunath, K. Sathish Kumar

Abstract: Seismic isolation is an alternative to conventional design methods for dealing with earthquake loadings in relatively high frequency structures, especially in low to medium rise buildings. One of the goals of seismic isolation is to shift the fundamental frequency of the structure away from the dominant frequencies of seismic excitations and fundamental frequency of the fixed base structure. This innovative design approach aims mainly at the isolation of a structure from the supporting ground, usually in the horizontal directions in order to reduce the transmission of the earthquake motion to the super structure. In this paper seismic analysis performed for a low to medium rise fixed base building and it was observed that the fundamental time period of the fixed system are typically in the resonance range of 0.1 sec. to 2.0 sec. This results in amplification of the ground acceleration causing severe damage to structures and their contents. To avoid such a situation, the period must be lengthened, by increasing the flexibility of the structure by introducing seismic base isolators between the foundation and super structures. A six storey structure under both fixed base and seismically isolated boundary conditions is studied to demonstrate the effectiveness of seismic isolation. The comparative result shows that maximum floor acceleration, inter-storey drifts and storey shear forces are reduced substantially for seismically isolated structure.

Keywords: Seismic base isolation, Seismic resistant design, Lead rubber bearings, Response spectrum analysis, Time period.

DOI: https://doi.org/10.15623/ijret.2013.0213001