Upper Bound Limit Analysis of Pipe Elbow

The non-differentiability of the plastic dissipation calculated through the Von-Mises yield function leads to convergence difficulties when using mathematical programming to solve upper bound limit analysis of pipe elbow. This problem is avoided replacing the plastic dissipation by the strain energy of a ficticious elastic-plastic material with a nearly infinite Young modular. The paper provides a mathematical programming fomulation for upper bound limit analysis of pipe elbow.