ANALYSIS OF PILED RAFT FOUNDATION USING FEM

Abstract

Piled raft foundations provide an economical foundation option for circumstances where the performance of the raft alone does not satisfy the design requirements. Under these situations, the addition of a limited number of piles may improve the ultimate load capacity, the settlement and differential settlement performance, and the required thickness of the raft. The whole study is divided into four parts, first is analysis of raft or unpiled raft only; second is analysis of equivalent raft in which pile is not introduced but at pile point extra spring is attached (simplified method); third is linear analysis of piled raft and last is non linear analysis of piled raft. The objective of this study is to observe the effect of raft thickness, pile diameter and pile •length on the maximum displacement of piled raft system, differential settlement, maximum bending moment of raft and axial load carried by pile with the help of parametric study. For Finite Element Analysis, raft is modeled as thick plate resting on Winkler foundation and pile as a beam. Four noded, isoparametric rectangular element with five degree of freedom per node for plate and two noded, beam element with five degree of freedom per node for pile are considered in the development of finite element formulation. A computer software CAD-PR (Computer Aided Design for Piled Raft) for the analysis of piled raft system using finite element method has been developed in VISUAL BASIC with FORTRAN. For result verification, pile raft has been also analysis by commercial software.STAAD-PRO and SAFE.