The response of structures in static and dynamic conditions deeply depends on soil-structure interaction (SSI). The soil-structure interaction can be analysed by means of the soil stiffness functions. The classic stiffness approach comes from elastic analysis and does not take into account soil nonlinearity. This paper deals with the effects of soil nonlinearity in the formulation of new stiffness functions for a shear wall with a shallow foundation. This type of structure can be used for strengthening at low cost buildings against earthquakes. The analysis of the whole soil, foundation and shear wall system behaviour in static and pseudo-static conditions is carried out by means of a nonlinear finite element code. The soil constitutive model is hyperbolic during the loading path and linearly elastic during the unloading-reloading paths. The numerical analysis allows us to estimate nonlinear laws for the vertical, horizontal and rocking stiffnesses involved in the soil-structure interaction. The numerical analysis is performed for various foundation embedments and soil conditions. The results should be of great use in the analysis of soil-structure interaction not only for shear walls, but also for silos, tall towers and cantilevers bridge piers, for which the deformability and nonlinearity of the soil supporting the structure are particularly relevant.
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