Effect of tangential plasticity on structural response under non-proportional cyclic loading

In an attempt to correct the unrealistic material stiffness predicted by elastoplastic models which adopt an associative flow rule, this paper introduces an innovative technique for the computation of the inelastic contributions generated in a non-proportional loading path. The formulation of these inelastic contributions takes into account the plastic response along the direction normal to the plastic potential, neglecting the irreversible stretch caused by the tangential component of the stress rate. Here, the introduction of tangential plasticity, in combination with the return mapping technique, eliminates this drawback, allowing fast and accurate computation. The present paper focuses on the evaluation of the load-carrying capacity of a steel bridge pier, indicating the necessity of considering the additional tangential plasticity term for a correct description of the structural response.