Finite Element Analysis for
Frame Foundation Soil Interaction

 

Dilip Kumar Maharaj

Assistant Professor, Civil Engineering Group
Birla Institute of Technology and Science, Pilani, Rajasthan, India
e-mail: dilip_maharaj@yahoo.com, dkm@bits-pilani.ac.in

A. Amruthavalli and K. Nishamathi

Students, Civil Engineering Group, Birla Institute
of Technology and Science, Pilani, Rajasthan, India

ABSTRACT

In this paper the frame raft soil interaction has been analysed by finite element method. The frame and raft have been considered as an elastic material while the soil has been modeled as an elastoplastic material by Drucker-Prager Yield criterion. The problem has been analysed by considering it as a plane strain problem. The frame has been considered at each meter location in the transverse direction. The raft and soil have been discretized into four noded isoparametric elements while the frame members have been discretized into two dimensional truss elements in the finite element analysis. Newton Raphson Iterative Procedure has been used to solve the nonlinear finite element equation. The effect of raft flexibility and rigidity on raft and frame, and the effect of frame stiffness on flexibility of raft have been analysed. The effect of flexibility of raft foundation has been found to increase the internal forces in the superstructure. The foundation has been found to undergo differential settlement due to its own flexibility. By increasing the superstructure stiffness the differential settlement of foundation has been found to be almost zero. The differential settlement has also been found to reduce to almost zero by increasing the foundation thickness. The overall settlement of foundation is found more when the stiffness of superstructure is increased keeping the foundation flexible than the case when the foundation stiffness is increased keeping the superstructure flexible.

Keywords: Raft, Frame, Analysis, FEM, Flexibility, Rigidity

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