SEISMIC PERFORMANCE EVALUATION OF RC FRAMED STRUCTURE CONSIDERING SOIL STRUCTURE INTERACTION

Abstract

Damages caused by a seismic event depend to a great extent on the features of the strong ground motions, these motions reflect primarily from factors such as source characteristics. Propagation wave path and local site conditions. In the normal design practice all will consider building frame as a fixed base but in actual case the flexible nature of soil allows the foundation for movement. Soil structure interaction (SSI) plays an important role in earthquake resistant design of structure. However, SSI analysis has only been applied in a few building projects because the fixed base condition is considered to provide a conservative estimation for the response of buildings under seismic loads. In this study, the seismic response of the structure is observed considering soil structure interaction (SSI) from its actual soil condition. This research focuses to know the effect of SSI on the response of buildings on its actual soil condition subjected to earthquake ground motion acceleration. Here, RC framed buildings G+2, G+5 and G+8 have been taken and are located at Seismic Zone 5. Taking into account the actual soil condition of building site, this study provides idea on the soil structure interaction on RC building. These buildings are analyzed as a bare frame and as infill frame using Equivalent diagonal Strut approach from FEMA356. Direct and substructure approaches are used to incorporate soil structure interaction in the analysis. The properties of springs are calculated for different standard penetration test (SPT) values and springs are assigned for footing for the substructure approach. Entire soil foundation-structure system is modelled and analyzed in single step for direct approach. Dynamic behavior of the structures with SSI is studied. Results are deduced from the following parameters i.e. joint displacement, storey drift fundamental time period and base shear. This thesis study is focused on the observations and results obtained from the building cases considered. Soil condition of site and soil depth from ground level highly influenced response of the structure. iv Static, modal, time history analysis are done to find variation in natural time period, base shear and deflection of structure by incorporating soil flexibility as compared to structure with conventional fixed base.