Effect of soil-pile raft-structure interaction on elastic and inelastic seismic behaviour

Abstract

Review of literature in the field of soil-pile raft-structure interaction indicates that considerable research effort was rendered towards to achieve accuracy in dynamic soil structure interaction (DSSI) model. Interestingly, limited results are available for design response of whole structural system. It is relevant to mention that pile damage (bending) has become a cause of distress in structures. In this context, an effort is devoted in the present paper to see whether DSSI have an adverse effect on elastic as well as inelastic behaviour in superstructure and foundation. This becomes possible through adopting a simplified substructure based DSSI modelling approach. Main focus of the present work is nonlinear seismic response of the whole structure with emphasis on consideration of material nonlinearity in both pile and soil which may contribute in salient design inputs towards performance based design of the whole structural system. Study reveals that consideration of DSSI condition results in inelastic deformation of superstructure and it exhibits marginal increase at higher stories. On the other hand significant increase in deformation at ground storey columns is observed if pile is restricted to deform within elastic range. In fact, initiation of smaller inelastic deformation of pile will lead to further increment in storey displacement, while such storey deformation will gradually decrease with higher inelastic range of deformation in piles and may be beneficial for superstructure system. Hence, designing of pile members with high ductility may reduce the seismic risk of failure of superstructure system. This physical insight may be an important consideration for performance based seismic design of structures.