Effect of soil-structure interaction on inelastic displacement ratios of degrading structures

This study presents an evaluation of inelastic displacement ratios for degraded structures considering soil-structure interaction (SSI). In this regard, a wide variety of effective parameters of hysteresis models and soil-structure systems are considered. Four different hysteretic models a) bilinear, b) modified Clough, c) stiffness degrading, and d) strength-stiffness degrading, are assigned to represent force-displacement response of super-structure. The supporting soil is modeled using the concept of cone models. Inelastic displacement ratios were computed for 12,000 soil-structure models with periods between 0.1 and 5 s when subjected to 19 strong ground motions recorded on NEHRP site class D. In addition, a parametric investigation is performed to evaluate the parameters that could affect nonlinear response of structures with strength-stiffness degrading hysteretic model. It is observed that generally SSI increases the inelastic displacement ratios with exception of very short period structures. Also, it is demonstrated that the soil-structure systems with stiffness degrading hysteresis model in short period range could experience larger inelastic displacement compare to those in non-degraded soil-structure systems. In particular, the SSI substantially increases inelastic displacement ratios of strength-stiffness degrading structures.