Importance of soil material damping in seismic responses of soil-MDOF structure systems

Abstract

In this study, the role of soil material damping in the engineering demand parameters (EDPs) of soil-structure systems is investigated. For this purpose, a superstructure is modeled as a two-dimensional nonlinear multi-story shear building. The soil beneath the foundation is simulated based on the concept of the cone model. The effects of various parameters are evaluated using the relative reduction ratios between demands in the presence of soil material damping and in its absence (radiation damping only). The results demonstrate that as the number of stories increases, the effects of soil material damping on the responses become more pronounced. Moreover, in the case of slender structures and higher structural ductility, the effects of soil material damping are governing in comparison to those of radiation damping. Generally, the consequences of soil material damping on the displacement demands are greater than those on the force demands. Furthermore, the roof displacement demands of the superstructure are more affected by soil material damping than by the maximum story drift angle response.