Seismic soil structure interaction response of elastic and inelastic moment resisting framed structures on embedded rafts

Abstract

A structure subjected to operational dynamic loads or moderate levels of ground shaking is expected to remain elastic. However under severe earthquakes, which are not very frequent, the same structure is designed to exhibit inelastic behaviour and sustain some damage so as to achieve an economical design. This dual strategy of seismic design makes understanding of elastic as well as inelastic behaviour of structures important. The present study devises an algorithm to assess effects of soil-structure interaction on elastic and inelastic seismic response of structures with kinematic hardening using the substructure approach. The critical step involved in this approach is the determination of dynamic impedance functions. The dynamic impedance functions have been obtained from literature. Wherever required, plots in Gazetas (1991) have been digitized to obtain polynomial expressions. The dynamic analyses on SDOF idealizations of structures have been performed in MATLAB using Newmark γ-β method. Effects of few engineering design parameters, which encompass material and geometrical properties of a soil-structure system, on the structural response of SSI systems have also been explored. The present study is restricted to moment resisting framed reinforced concrete buildings founded on embedded raft foundations.