Seismic soil structure interaction analysis of piled raft supported asymmetrical buildings

Abstract

Super structures are mostly founded on layers of soil unless bedrock is very close to the ground surface and shows the different behavior for different supporting domain. This difference in behavior referred to as soil-structure interaction (SSI), which if not taken into account in the analysis and design properly, the accuracy in assessing the structural safety, facing earthquakes, could not be reliable. The seismic soil structure interaction analysis is primarily demotivated in the practices due to complexity and its numerical size. The soil structure interaction problem is computationally very expensive due to big size which includes interfaces, nonlinear soil behavior, and structure. This cost has been exponentially increasing with the volume of soil, interfaces area and structure geometry is increasing. In case of pile foundation the soil domain is needed to consider deeper and wider thus it is essential to reduce the model with some techniques.In this study finite element program for dynamic analysis has been developed using C++, a versatile low level object oriented language. The study has been focused to reduce the foundation system by replacing the pile group with the equivalent pier method. This approach for soil-structure interaction analysis has been fully investigated for system displacement and stresses for different earthquake loading ranging from medium to large and different soil condition for L,C and T type mid rise R.C.C. building. The applicability of the equivalent pier method has been checked for different set of location of a pier in the plan area and the suitable pier combination has been obtained which gives the optimum deviational response of the superstructure. The results are estimated with the view of the significance of SSI analysis for the particular loading and local soil condition, applicability of the Equivalent Pier Method to reduce the computational efforts and the complexity in modeling, soil structure interaction effect on the responses of the superstructure.