Effects of Soil-Structure Interaction on the Linear and Nonlinear Seismic Behaviour of Coupled Wall-Frame Systems

The effects of Soil-Structure Interaction (SSI) on the response of coupled wall-frame structures on pile foundations are investigated. The analysis methodology based on the substructure method is re-called focusing on the modelling of pile group foundations. The iner-tial interaction analysis is performed in the time domain by using a fi-nite element model of the superstructure and suitable Lumped Pa-rameter Models (LPMs) are implemented to reproduce the frequency-dependent compliance of the soil-foundation systems. The effects of SSI are evaluated by considering realistic case studies consisting of 6-storey 4-bay wall-frame structures founded on piles. Moderate and strong seismic actions are simulated employing real and artificial earthquakes. The superstructure is assumed to behave linearly under moderate shakings; on the other hand, the nonlinear structural behav-iour is accounted for in the case of strong earthquakes. Comparisons of the results obtained considering compliant base and fixed base models are presented by addressing the effects of SSI on the main re-sponse quantities of linear and nonlinear structures. SSI effects on displacements, inter-storey drifts and base shears are discussed and, with reference to the nonlinear structures, effects on the ductility de-mand and the evolution of dissipative mechanisms are investigated by considering earthquakes with increasing intensity