Seismic Displacement Demand of a Mid-Rise RC Building Considering Soil Structure Interaction

Abstract

This study aims to evaluate the effect of soil structure interaction and the differences in linear and nonlinear modelling of the structure on seismic response. For this purpose, SSI and fixed base models of 7-story building were used. Both linear and nonlinear behavior of the building are taken into account for comparison. The findings obviously indicate large variation in displacement demands depending on ground motion record, soil type, consideration of soil structure interaction and linear and nonlinear structure modelling. The displacement demands tend to increase for softer soils except few cases, especially for fixed base models. Significant differences are obvious for linear and nonlinear building models of fixed base case. The evaluation of obtained results and observations in the current study clearly indicate that the effects of SSI approach depend on dynamic characteristics of soil and structure. While soil deformations influence the seismic demands of structure in positive way for linear models, these effects are more complex for nonlinear models. It is difficult to mention about certain trend for nonlinear models. It should be also kept in mind that linear fixed base models are inappropriate for dynamic analysis due to high sensitivity of dynamic amplification and the use of fixed base linear models may cause inaccurate seismic demand estimates. The outcomes and observations emphasize that the demand estimates are independent from the fixed base or SSI approaches and linear or nonlinear models for stiffer soils. All combinations provide reasonable demand estimates. However, the modelling approach becomes extremely important for softer soils. The best approach seems to be SSI with nonlinear modelling. The fixed base with nonlinear modelling also provides acceptable estimates.