Seismic Analysis for Influence of Ground Flexibility on Irregular Shaped Buildings

Abstract

In most of the designs of structures, the buildings are analyzed by assigning fixity at base, buildings are idealized to rest on hard soil. The present study discusses the importance of soil stiffness and the effect of flexibility of soil stiffness on the seismic performance on irregular shaped building. H, L, Rectangular & T shape building for G+5, G+10 and G+15 storey with and without friction dampers is considered. Flexibility of soil causes increase in lateral natural period of structural system due to overall decrease in stiffness. Increase in natural time period significantly alters the seismic response of the building. Hence, in this paper the effect of flexible soil on the seismic performance of irregular shaped buildings and their dynamic behaviour from Pushover analysis. Gazetas model is used for computing the stiffness of soil and the foundation resting on soil is considered as a spring. ETABS 9.7 software is used for analysis, design and pushover analysis. It is observed that modulus of soil has considerable effect on natural time period and overall performance of structural system, use of friction damper reduces natural period. Hence soil flexibility place an important role instead of idealization of rigid base in seismic analysis.