Hysteretic Energy Demand of Soil-Structure Systems

The effect of soil-structure Interaction on hysteretic energy demand of buildings under an ensemble of 24 earthquake ground motions recorded on alluvium sites is investigated. The building is modeled as a single-degree-of-freedom oscillator resting on flexible soil. The soil beneath the building is considered as a homogeneous elastic half space and is modeled via the concept of Cone Models. A parametric study is done using the aspect ratio of the building as well as a non-dimensional frequency as a representative of the structure to soil stiffness ratio. Making use of an optimization procedure, non-dimensional scaling indices are derived to minimize the average coefficient of variation of energy spectra. This is done separately for each spectral region. The results due to individual scaled records are then averaged and presented in the form of energy spectra. It was concluded that generally the dissipated hysteretic energy decreases under SSI effect except for the rare cases of short-period slender buildings. The energy drop is more significant for squatty buildings located on soft soils. The variations are more sensible in the acceleration and velocity spectral regions and usually minor in the displacement region.