Numerical determination of limit loads for three-dimensional structures using boundary element method

Based on the static limit analysis theorem, a solution procedure for limit analysis of three-dimensional (3-D) structures is established making use of conventional boundary element method (BEM) rather than of finite element method (FEM). The self-equilibrium stress fields are expressed by linear combination of several basic self-equilibrium stress fields with parameters to be determined. These basic self-equilibrium stress fields are elastic responses of the body to imposed permanent strains obtained through elastic-plastic incremental analysis by three-dimensional boundary element method (3-D BEM). The Complex method is used to directly solve the resulting nonlinear programming problem and to determine the maximal load amplifier. The numerical results show that it is efficient and accurate to solve 3-D limit analysis problems by using BEM and the Complex method.