INFLUENCE OF SOIL STRUCTURE INTERACTION ON HYSTERETIC ENERGY DEMAND OF STIFFNESS DEGRADING STRUCTURES

Hysteretic energy is related to the inelastic deformation the structure undergoes during the ground motion. Unless otherwise dissipated by means of some mechanism, hysteretic energy could impose permanent damage to the structure. This paper aims to study the influence of soil-structure interaction on plastic energy demand spectra of soilshallow-foundation structure subjected to a family of strong ground motions recorded on alluvium soil. The superstructure is modeled as a single-degree-of-freedom (SDOF) oscillator with Modified Clough stiffness degrading model resting on flexible soil. The soil beneath the superstructure is considered as a homogeneous elastic half space and is modeled through the concept of Cone shallow foundation Models. A parametric study is carried out for different soilstructure systems with various aspect ratios of the building as well as non-dimensional frequency as a representative of the structure-to-soil stiffness ratio having a wide range of fundamental fixed-base period and target ductility demand values under an ensemble of 19 earthquake ground motions. Results show that generally for the structure located on softer soils severe dissipated energy drop will be observed with respect to the corresponding fixed-base system. The only exception is for the case of short period slender buildings in which the hysteretic energy demand of soil-structure systems could be considerably larger than that of their fixed-base counterparts.