Deflection modification factors of multistory buildings considering soil-structure interaction

In this investigation, attempts are made to examine the effects of soil-structure interaction on the deflection modification factor of multistory buildings and to clarify the role of deformable soil on this factor. A comprehensive study is conducted to investigate the effect of inertial interaction on displacement demand ratios in soil-structure systems with different structural characteristics and various non-dimensional parameters, using a simplified interacting model. A two-step regression analysis of the nonlinear, dynamic computer simulation results obtained, leads to a reliable and accurate formula for predicting deflection modification factors that incorporate foundation flexibility. The results illustrate that the application of deflection modification factors derived from fixed-base structures can lead to unsafe evaluation of the structures on soft soil. The proposed formula provides a useful tool for design engineers to incorporate the effect of soil–structure interaction into the evaluation of structural deformations.