Abstract: Recent studies show that the effects of Soil Structure Interaction (SSI) may be detrimental to the seismic response of structure and neglecting SSI in analysis may lead to un-conservative design. Despite this, the conventional design procedure usually involves assumption of fixity at the base of foundation neglecting the flexibility of the foundation, the compressibility of the underneath soil and, consequently, the effect of foundation settlement. Hence the SSI analysis of a multi-storey building is the main focus of this work; the effects of SSI are analysed for the building considered by using springs to model the foundation. In the present work, the analysis of the building (G+9) with and without considering infill has been carried out by incorporating the effect of SSI by springs for three different types of soils such as silty sand, dense sand and dense gravel, and three different earthquake intensities according to IS 1893:2002 using ETABS. The stiffness of the springs are determined by the formulas given by Gazetas and Mylonkais. The storey lateral displacements are evaluated. From the study it has been observed that as the soil stiffness is increasing, the storey lateral displacements are decreasing. Silty sand having less stiffness has pronounced effect on the seismic response. Dense gravel having high stiffness has almost the same effect of fixed base model.

Keywords: Storey Lateral Displacement, Soil Structure Interaction, ETABS, Stiffness.