A computationally efficient method for the limit elastoplastic analysis of space frames

A computationally efficient method for the first order step by step limit analysis of space frames is presented based on the generalized plastic node method. The non-linear yield surface is approximated by a multi-faceted surface, thus avoiding the iterative formulation at each load step. A second internal and homothetic to the initial yield surface is implemented which create a plastic zone for the activation of the plastic modes. The solution of the linear equilibrium equation at each load step is obtained with the preconditioned conjugate gradient method using some recent developments with respect to improved matrix handling techniques and efficient preconditioning matrices.