ABSTRACT
The influence of dynamic Soil-Structure-Interaction (SSI) phenomena on the response of structures under dynamic loading is widely recognised. These phenomena are more impactful on structures that are founded on soft soil sites, where soil nonlinearity can prevail. The present study examines this aspect by the means of three-dimensional nonlinear finite element analyses of real-scale free-vibration experiments on a steel frame structure. The structure has outer dimensions of 3×3×5m and is rested on a shallow foundation over a soft soil deposit. The numerical analyses focus on modelling experiments of different magnitude excitation forces, to allow the investigation of the SSI system for a wide strain range. Cyclic nonlinear models, which are typically used in numerical analysis to predict the hysteretic behaviour of soils, can simulate well either the stiffness degradation (G-γ) or the damping evolution (D-γ) with cyclic shear strain. Experimental strong motion data are compared against numerical results of analyses that adopt different G-γ-D curves for the shallow foundation soil. This investigation reveals that the choice of G-γ-D curves affects significantly the SSI free-vibration response, highlighting the importance of modelling the nonlinear behaviour of shallow soil appropriately. It also suggests that prioritising the calibration of the D-γ curve over G-γ is more applicable for most of the modelled experiments.
