Seismic soil-structure interaction of buildings on hill slopes

In hilly regions, engineered construction is constrained by local topography resulting in the adoption of either a step-back or step-back-set-back configuration as a structural form for buildings. The adopted form invariably results in a structure which is irregular by virtue of varying column heights leading to torsion and increased shear during seismic ground motion. To capture the real behavior of buildings on hill slope a 3-D analysis of the building is required. In the present study, static pushover analysis and Response spectrum analysis (RSA) have been conducted on five building i.e. three step back buildings and two step back-set back buildings with varying support conditions. These buildings have been analyzed for different soil conditions (hard, medium and soft soils) idealized by equivalent springs. The response parameters, i.e. total base shear (V), displacement from pushover analysis (δ _{performance point}), displacement from RSA (δ _elastic) and response correction factor (R’) have been studied with respect to fixed base analysis to compare the effect of soil springs. In general it is found that response reduction factor decreases with increasing time period, but is expected to be constant beyond a certain value of time period.