Seismic Response of RC Bare Frame and Shear Wall Frames With and Without Considering Soil Structure Interaction in Buildings

The significance of incorporating soil-structure interaction effect in the analysis and design of RC frame buildings is increasingly recognized but still not penetrated to the grass root level owing to various complexities involved. It is well established fact that the soil-structure interaction effect considerably influence the design of multi-storey buildings subjected to lateral seismic loads. The shear walls are often provided in such buildings to increase the lateral stability to resist seismic lateral loads. In the present work, the linear soil-structure analysis of a G+5 storey RC shear wall building frame resting on raft footing and supported by deformable soil is presented. The finite element modelling and analysis is carried out using SAP2000 software under gravity loads as well as under seismic loads. The interaction analysis is carried out with and without shear wall to investigate the effect of inclusion of shear wall on the forces in the footing due to settlement of soil mass. The frame and soil mass both are considered to behave in linear elastic manner. It is observed that the soil-structure interaction effect significantly alters the time period, frequency and base shear of the building due to the soil settlement. The non-interaction analysis of space- frame-shear wall suggests that the presence of shear wall significantly reduces time period and displacement of the building but the interaction effect causes restoration of the time period and displacement to a great extent. Keyword: soil-structure interaction, SAP2000, bare frame, shear wall, time history analysis, time period, natural frequency, displacement, base shear. The conventional structural analysis of a RC bare frame is carried out assuming foundation resting on unyielding supports. The analysis is carried out by considering bottom end of the columns fixed and neglecting the effect of soil deformations. In reality, any building frame rests on deformable soil resulting in redistribution of forces and moments due to soil-structure interaction. Thus, conventional analysis is unrealistic and may be unsafe. The interaction effect is more pronounced in case of multi-storeyed buildings due to heavy loads and may become further aggravated when such buildings are subjected to seismic loads. The shear walls are usually provided in such situation to resist seismic lateral loads. The behaviour of shear walls in the space frame during soil structure interaction is a matter of high concern. In the present work, 3-D soil- structure interaction analysis has been carried out for a G+5storey RC framed building with raft footing under gravity as well as seismic loads using finite element software SAP2000. The analysis has been carried out considering space frame with and without shear walls located at the corners of the building. Here time history analysis is carried out using Bhuj earthquake data. The model is easily extendable to any configuration of space frame and shear wall as full 3-D space frame is considered for analysis. The results of conventional i.e. non interaction analysis as well as linear interaction analysis are compared for the space frame with and without shear wall to investigate the effect of displacement, time period, base shear and stresses in the footing.