Seismic Soil Structure Interaction of a Midrise Frame Structure

Abstract

Earthquakes have occurred for millions of years and will continue in the future affecting millions of lives, thousands infrastructure and costing billions of dollars. Seismic soil structure interaction is the process in which the structure rested on the ground and subjected to an earthquake is affected by the response of the soil medium beneath it having its own characteristics. Thus, soil structure interaction response is dictated by the interaction between the structure, foundation and underlying soil or rock. To clarify the contribution of the seismic soil structure interaction, 3D time history finite element models of 15 story concrete frame building were performed using Abaqus under Kocaeli’s Mw = 7.5 strong ground motion. The effects of soil boundary limits, mat thickness and soil linearity were investigated. To demonstrate the importance of modeling correct soil structure interaction problems, the numerical analysis was carried out for three cases: (1) a fixed-base structure, (2) a structure rested on silty sandy soil, and (3) a structure supported by raft foundation and rested on silty sandy soil. The results, presented in terms of the structural lateral deflection and base shear versus time, show that soil structure interaction effects should be evaluated when the maximum lateral deflection is obtained at top of the structure regardless when it occurred as well as at maximum absolute lateral deflection at each level. Moreover, excluding soil structure interaction effects may result in inadequate structural safety for the frame building rested on silty sandy soil and considering linear soil properties may result in non-economical structural design.