Improvement of the model proposed by Menegotto and Pinto for steel

The model proposed by Menegotto and Pinto is widely used to simulate the cyclic response of steel structures and steel bars of reinforced concrete structures. In the early 1980s, Filippou et al. improved the original model by introducing isotropic hardening and highlighted a flaw in the original formulation. Specifically, these researchers observed that if partial unloading takes place at strains lower than the maximum value the reloading path provides forces that are higher than those expected. Notwithstanding, Filippou et al. deemed that these errors were not particularly significant and did not propose any modification to the formulation of the model. In the opinion of the writers, this conclusion may be questionable and thus an improved version of the Menegotto and Pinto model is proposed here. In particular, the abovementioned flaw is eliminated and the improvement of this model over the original Menegotto and Pinto model is shown.