Evaluation of Soil-Structure Interaction for Different RC Structural Systems and Foundation Sizes

Abstract Past earthquakes and contemporary research reveal that dynamic soil-structure interaction (SSI) could significantly alter the structural response of a building during an earthquake. These effects are functions of several parameters, including structural system, foundation type and geotechnical characteristics of the subsoil. Previous studies discovered that SSI effects are more prominent for structures supported by shallow foundations. However, increasing the foundation size for high-rise buildings tends to decrease the SSI effects in lateral deflections and foundation rocking. Further, the structural response of wall-frame structures differs from Moment-Resisting Frame (MRF) structural system. The present article extends earlier findings to investigate the influences of shallow foundation size on the seismic response of short and medium heights of reinforced concrete buildings resting on soft soil deposits. In addition, the inertial soil-structure interaction effects on MRF and wall-frame systems are studied and compared. A nonlinear Winkler foundation model (BNWF) is adopted to represent the soil domain. The model allows accounting for plastic deformation in the subsoil and considers the soil damping. The structural elements are modelled based on distributed plasticity mechanism to capture the inelastic response of the structures. A 3-storey, 6-storey and 12-storey building with various foundation sizes and different structural systems are numerically simulated in OpenSees software. The buildings are subjected to five moderate earthquake records for time history analysis in the time domain. The results are expressed in terms of period lengthening, lateral deflection, inter-storey drift, and base shear forces. The results reveal a noticeable influence of foundation size on dynamic characteristics and seismic response of MRF structures. Increasing foundation length decreases the structures’ lateral deflection and base shear forces. However, these effects are less observable for the short-height structure. On the other hand, the wall-frame system is relatively more influenced by SSI effects than the MRF system. The effects of period elongation and increasing base shear forces due to SSI are more noticeable for wall-frame systems, and these effects are maximum for stiffer structures. Similarly, the increase in maximum lateral displacement and storey drift is higher in wall-frame buildings compared to MRF structures, particularly in the lower stories of the building.