Lower bound limit analysis of three-dimensional elastoplastic structures by boundary element method

Based on the lower bound theorem of limit analysis, a solution procedure for limit analysis of three-dimensional elastoplastic structures was established using conventional boundary element method (BEM). The elastic stress field for lower bound limit analysis was computed directly by three-dimensional boundary element method (3-D BEM). The self equilibrium stress field was constructed by the linear combination of several self-equilibrium "basis vectors" which can be computed by elastic-plastic incremental iteration of 3-D BEM analysis. The lower bound limit analysis problem was finally reduced to a series of nonlinear programming sub-problems with relatively few optimal variables. The complex method was used to solve the nonlinear programming sub-problems. The numerical results show that the present solution procedure has good accuracy and high efficiency.