Effects of Soil Structure Interaction (SSI) on the design of Reinforced Concrete Buildings

Abstract

Normally reinforced concrete buildings are analyzed and designed as fixed or hinged supports which are
assigned to columns, ignoring foundation flexibility and its interaction with soil underneath and around it. To investigate
the response of buildings under seismic loads the fixed base condition is considered to provide a conservative estimation
that’s why the SSI analysis is generally ignored. The fixed base assumption adopted by the structural engineers is not
always cost effective and conservative, especially in the case of soft soils supporting rigid buildings. The design outputs
such as fundamental time period, Inter-story drifts, story lateral displacements and beam & column design is compared
for flexible and fix based supports. The fundamental time period, inter-story drift, lateral displacement are not that much
substantial but the lateral displacement must be considered for pounding analysis of adjacent buildings. The local
differences in flexure reinforcement of columns in fixed base and flexible base is significant