Influence of Soil Nonlinearities on Dynamic Soil-Structure Interaction

For moderate or strong seismic events, the maximum strains can easily reach the elastic limit of the soil behavior. Considering soilstructure interaction, the nonlinear effects may change the soil stiffness at the base of the structure and the energy dissipation into the soil. To take into account the nonlinearity of the soil in the dynamic soil-structure interaction (DSSI), a 3D constitutive model, proposed by Iwan, is used to investigate DSSI in the framework of the Finite Element Method. The model accounts for the nonlinear hysteretic behavior of soils and only needs the shear modulus degradation curve to characterize the soil behavior. This feature is very important since complex constitutive models generally involve numerous mechanical parameters difficult to characterize experimentally. A parametric study is carried out for different types of structures to characterize nonlinear effects in the time domain. Through these numerical simulations, the nonlinear behavior of the soil is shown to have beneficial or detrimental effects on the dynamic response of the structure depending on the way the interaction process is modified: change in the amplitude and frequency content of the waves propagated into the soil, fundamental frequency of the response of the soil-structure system and energy dissipation