Spread-of-plasticity analysis of three-dimensional steel frames

A second-order spread-of-plasticity analysis program has been developed for analysing three-dimensional (3-D) steel frames. Material nonlinearity is modelled through the von Mises yield criterion in conjunction with the associated flow rule and the assumption of isotropic hardening. Gradual yielding is modelled through numerical integration of the material points on the cross-sections, which are located at the selected integration points along the member length. A mixed element formulation is proposed for analysing large-scale framework analysis. Established benchmark results are used to verify the proposed spread-of-plasticity analysis. The inelastic behaviour of a 3-D steel frame is investigated, and the computing efficiency and accuracy of using the mixed-element approach for advanced analysis of large-scale framework is illustrated.