Most of the research conducted for soil-structure interaction analysis of structures are assuming the linear behavior of soil. It is well known that during strong ground excitations the soil adjacent to the structure behaves highly non-linear. The nonlinear soil behavior affects the soil-structure interaction in a complex way especially because of the inadequacy in modeling the unbounded soil medium. In the case where an elastic soil behavior is assumed, the surface motion will be amplified proportionally to the input motion. However, in reality the amplitude and frequency content of the response are modified due to the soil’s stiffness degradation and higher energy dissipation. The present work deals with the influence of soil non-linearity, introduced by hysteretic behavior of near-field soil, on the soil-foundation-structure interaction phenomena. The objective is to reveal the beneficial or detrimental effects of the non-linear SSI concerning both the drift and internal forces of structures with underground storeys. To asses non-linear soil-structure a realistic non-linear soil model is incorporated into the finite difference FLAC software. To better understanding the non-linear dynamic SSI, interface elements are also used between the near-field soil and basement walls. Throughout a parametric study, some non-linear seismic analyses were performed to demonstrate the effectiveness of the affecting parameters in response of the structure. The results showed much difference on seismic response of the structure such as drift, settlement, developing pressure around the basement walls and base shear when the non-linear soil-structure interaction are considered. It was shown than the structured response highly depends on the soil constitutive model. Also it was demonstrated that due to acting interface elements, the base shear could be higher than the corresponding value for linear anaysis.
