Performance evaluation of simplified SSI models during strong earthquake events and nonlinear soil response

Soil–structure interaction (SSI) plays a major role in the seismic response of buildings placed on soft soil deposits, especially when subjected to strong ground motions where nonlinear soil behaviour becomes critical. Accurate modelling of these interactions is essential for reliable seismic design. This study evaluates the performance of three simplified SSI models in predicting building response under varying earthquake intensities and nonlinear soil conditions. An experimentally validated FE model with an advanced nonlinear soil constitutive model is employed as a benchmark model for the assessment process. The analysis focuses on the accuracy and applicability of these models to capture key seismic responses, including lateral displacement, inter-storey drift, base shear, foundation rocking, and settlement. Results show that while linear models are sufficiently accurate for low-intensity shaking, they become unreliable at higher intensities due to their inability to capture nonlinear soil behaviour. In contrast, the BNWF model maintains better accuracy across all intensities, though it slightly underestimates responses at higher amplitudes. The findings highlight the importance of selecting appropriate SSI models, especially in scenarios involving significant soil nonlinearity.