ANALYSIS OF SOIL STRUCTURE SYSTEMS SUBJECT TO EARTHQUAKES

Abstract

The method most commonly used by structural engineers, for the analysis of buildings, designed to resist earthquake forces, assumes the structure to be attached to a rigid foundation. Such a procedure tends to simplify the mathematical analysis of the problem, the basic assumption being that there is no interaction between the structure and the soil. The complete analysis, incorporating the effect of interaction is done only for very important structures like nuclear power plants. Rarely is the effect of interaction incorporated in the analysis of frames and if incorporated,,. it is generally done so, by using results of analytical solutions of rigid plate resting on elastic half space (thus neglecting cross—coupling between footings). The present study suggests a method of analysis for frame structures (long in one direction) using the finite element method. The effect of interaction due to earthquake forces is studied by varying structural and substructural parameters. It is observed that the response of a structure depends both on the soil properties and on structural para-meters like beam to column stiffness ratio, number of storeys, number of bays etc. It is concluded that soil—structure interaction effects should invariably be considered in important buildings.