Structure-soil-structure interaction effects on pounding vulnerability and force distribution between adjacent buildings

This study investigates structure-soil-structure interaction (SSSI) effects on foundation forces and settlements of adjacent reinforced concrete buildings under seismic loading. SAP2000 was incorporated for developing a 3D finite element model for analysing two identical three-story RC frame buildings with a 50 mm seismic gap between them. The study compares three scenarios: Non-Interaction Analysis (NIA) with fixed base, Soil-Structure Interaction (SSI) for a single building, and SSSI for two adjacent buildings on the same soil domain. Response spectrum analysis following IS 1893:2016 was implemented. The results show that SSSI significantly redistributes foundation forces, with reductions up to 7% in some footings and increment up to 13% in others compared to SSI conditions. Footings in alignment with adjacent buildings experience the most pronounced force amplifications. Settlement patterns under SSSI conditions show distinct asymmetry, with increment up to 15.8% under gravity loading and 7.6% under seismic loading compared to SSI conditions. These findings suggest that conventional fixed-base analysis may underestimate foundation forces and settlement values, potentially reducing effective seismic gaps and increasing pounding vulnerability. The research offers valuable insights for seismic design practices in densely populated urban environments where buildings are constructed in close proximity.