Influence of Soil-Structure Interaction on Seismic Behaviour of Mid-Rise Building using Non-Linear Time History Analysis.

Abstract

Soil-Structure Interaction (SSI) plays an important role in how buildings respond to earthquakes, especially mid-rise structures supported on different soil conditions. This study examines the seismic behaviour of a G+10 reinforced concrete building resting on soft, medium, and hard soils. The building was analysed in SAP2000 under both fixed-base and flexible-base conditions to capture the effect of soil flexibility. For the flexible-base models, springs were used to represent the stiffness of each soil type. To ensure realistic seismic loading, ground motions were scaled using the One-Step Scaling method, and nonlinear time history analysis was carried out to observe the building’s dynamic response. The results clearly show that buildings with flexible bases experience greater fundamental periods, base shear, overturning moments, lateral displacements, and storey drifts than fixed-base models. These effects are most noticeable on soft soil, where the increased flexibility amplifies the building’s response. Medium and hard soils also influence the behaviour, but the changes are less severe. Maximum storey drift occurs in the middle floors, highlighting potential areas for damage. These findings stress the importance of considering SSI in seismic design to avoid underestimating the real demands on a structure and to improve earthquake resilience.