Avaliação do comportamento inelástico de colunas e pórticos metálicos com flexão em torno do eixo de menor inércia

Abstract

This work presents an evaluation of the inelastic behavior of steel structures subjected to minor-axis bending. Profiles type I and compact cross-sections are considered. In these sections, the bent about weak axis presents important benefits, such as the ability to develop all of their plastic resistance without the occurrence of lateral torsional buckling. A nonlinear beam-column element formulation is adopted, in which the steel yielding process is accounted by the refined plastic-hinge method. In this method the effects of material yielding are captured by a parameter that reduces the structural member stiffness with the development of cross-section plastic regions. The tangent modulus approach is used to consider the stiffness degradation caused by the increase in internal forces. Second-order effects, residual stresses and geometric imperfections are also considered in analysis. To define the cross-section strength ultimate limit state, the study adopts strength surfaces that describe the interaction between internal forces - axial force and bending moment. The nonlinear equations at the structural system level are solved using the Newton-Raphson iterative strategy coupled with path-following methods. Isolated steel columns and portal frames are analyzed, and the results obtained are compared to those of other investigators. The comparison shows that the numerical methodology presented in this work is effective and can be used for predicting the behavior of steel structures with members under minor-axis bending.