Influence of Nonlinear Soil–Structure Interaction on the Seismic Response of a RC Floating Columns Structure with Geotechnical Isolation and Shear Wall Systems

Nonlinear soil properties are crucial in seismic structural responses, revealing the interdependence between soil and structure during seismic events. Floating column structures are significantly more vulnerable to seismic activity compared to traditional fixed-base structures due to soil–structure interaction (SSI). Despite the growing prevalence of reinforced concrete structures with floating columns in urban areas, their seismic performance and protection, especially under SSI effects, remain largely unexplored. This three-dimensional finite-element analysis study aims to enhance the seismic performance of reinforced floating column structures by introducing a novel approach that combines geotechnical seismic isolation (GSI) systems with sand–rubber mixtures (SRM) and shear wall systems. Soil nonlinearity was modeled using an advanced isotropic hardening elastoplastic hysteretic constitutive model. A parametric study evaluated the impact of GSI layer thickness, ground motion characteristics, and geogrid layers on the seismic demands of floating column structures. The analysis results show that a GSI-SRM layer with a thickness of 0.15B (where B is the width of the foundation), combined with double-layered geogrids and shear walls, significantly reduces seismic demands. This configuration lowers spectral acceleration and lateral story displacement by up to 40% and 36%, respectively, under SSI, and decreases base shear by 39% compared to fixed-base conditions.