INFLUENCE OF SOIL-STRUCTURE INTERACTION ON SEISMIC PERFORMANCE OF TALL BUILDINGS

Abstract

The interaction between a building and the supporting soil plays a critical role in determining structural behavior, especially during seismic events. This project focuses on evaluating the Soil-Structure Interaction (SSI) effects for a G+14 reinforced concrete building with a basement, situated in Delhi — a region classified under Seismic Zone IV according to IS 1893 (Part 1): 2016. While conventional analysis often assumes a fixed support at the foundation level, such assumptions can overlook the influence of soil flexibility on a building’s dynamic response. Using ETABS 20, the structure is modeled to include both the superstructure and basement levels. Soil flexibility is accounted for by introducing equivalent spring constants that simulate the supporting ground’s response under load. These constants are based on assumed geotechnical conditions typical of Delhi’s subsoil. The study examines how variations in soil stiffness affect key structural parameters such as lateral displacement, base shear, time period, and inter-story drift. Response spectrum analysis is used to compare the seismic behavior of the fixed- base model with that of models incorporating SSI. It is observed that neglecting soil compliance may result in either underestimating or overdesigning structural components. The study also provides insight into how SSI affects basement wall behavior due to lateral earth pressures. In conclusion, this research demonstrates the significance of including soil- structure interaction in high-rise structural models, especially for earthquake-prone zones. It also recommends the integration of structural software like ETABS with geotechnical tools such as PLAXIS for more refined SSI studies in future research.