BEHAVIOUR OF COMBINED PILE-RAFT FOUNDATION (CPRF) UNDER SEISMIC LOADING

Abstract

The combined pile-raft foundation (CPRF) is used worldwide, for high rise buildings, heavy dynamic machines and other engineering structures under vertical and lateral loading over past two decades. This is due to its effectual load sharing and interaction between its elements i.e. raft, pile and soil. However, CPRF under seismic loading is not much reported in literature. Therefore, Analysis of CPRF under seismic loading is examined to have lucid visualization in practical application. In present study, to investigate response of CPRF, a numerical model has been made in finite element software PLAXIS 3D with required material properties and interactions between its elements under real earthquake excitation. The numerical model used for this study was validated with experimental and numerical results reported in literature and a good agreement is found. Influence of the parameters such as pile-raft connection, Arias intensity and peak ground acceleration (PGA) of different ground motions, are considered for this analysis. The response of system is evaluated, in terms of response spectrum at raft and far field, Arias intensity and lateral displacement curves of different ground motions, bending moment, vertical and lateral displacement of piles. The model is also investigated under different PGA of a normalised and scaled ground motion. It is observed that Arias intensity and PGA of input ground motion have significant effect on the response of CPRF system (in terms of lateral displacement), compared to response of acceleration-time history obtained at top of system.