Numerical Simulation of Nonlinear Interaction of Soil, Superstructure and Thick Raft with Irregular Plan

Abstract

Of all types of foundation for tall buildings, thick raft is used most frequently nowadays in China. With the rapid progress of economy, tall buildings with various shapes have been constructed in recent years, thus promoted the developing of thick rafts with irregular plans. This paper presents a finite element method (FEM) based analysis for the interaction of soil, tall building superstructure, and raft foundation with a irregular plan. The irregular boundary is simulated as four nodes isoparametric element, Mindlin model for moderate thickness in which transverse shear is considered is used in order to improve the accuracy of calculation. The ground stiffness matrix is calculated by Boussinesq model and the nonlinear analysis is proposed to consider the foundation detach from soil. It is found from the investigation that the calculation accuracy of elastic half-space ground model can be improved by adopting the load test results and this make the results of calculation close to the experimental value. A finite element method program IRF is worked out to calculate the interaction of raft foundation and soil using FORTRAN90. The program SUPER is worked out using substructure can be used for calculating reduced superstructure stiffness matrix and reduced load vector. Four different types of irregular foundations are used as numerical examples, and the results of distribution of settlement and principle stresses of the foundation are briefly illustrated.