Influence of slope topography on soil-structure interaction during earthquakes

This article examines the effects of slope topography, soil non-linearity and soil-structure interaction (SSI) in hilly areas, where severe damage to hill buildings during past earthquakes were observed. Two-dimensional finite element analysis is carried out to simulate seismic response of hill buildings situated on the center of the slopes for three earthquake time histories. The influence of topographic amplification and SSI as a function of frequency of ground motion and site condition are examined. The present study shows significant ground motion amplification near the crest. It was found that the Seismic-Slope Topographic Amplification Factor (S-STAF) indicating the effect of slope on the seismic response, increases with the increase of slope angle and peak ground acceleration. However, S-STAF was increased by a margin as much as 30% when the non-linearity of the soil is considered. The effects of structural irregularity are also investigated by considering two types of buildings, (i) stepback and (ii) stepback and setback. Relative displacement of each story normalized with its height is reported as a drift ratio for two different slopes. The inter-story drift ratio of stepback building is slightly smaller than that of stepback and setback building. The seismic displacement of the slope increases significantly due to the presence of the building. The significant effect of SSI is observed with the increase of slope angle and this effect is much dependent on the earthquake characteristics. Further, period lengthening characteristics, seismic displacement, rocking and stress distribution of the footings of a stepback building on slopes are also investigated.