Improvement proposal for the Eurocode 3 rules about the plastic resistance of I-sections subjected to bending and axial force

Abstract

This paper proposes a new analytical criterion for the interaction between the resisting bending moment and axial force of steel I-sections bent over one of their main axes, in their plastic limit states, corresponding to the formation of a plastic hinge. The formulation of this criterion, based on an integration of the stress field over the whole cross-section area, took into account the influence of the cross-sections root fillets in the transition zones between the cross-section web and each one of its flanges. Therefore, this new criterion represents a more accurate theoretical solution when compared to other analytical criteria based on simplifying hypotheses, such as those adopted in some steel design codes and standards. Furthermore, it presents the advantages of its simplicity and common applicability to both cases of bending over the cross-section strong and weak axis. An application example shows the solving procedure of a design problem by means of this new criterion and by the Eurocode 3 rules. Then, a comparative study between the values provided by these two methods is presented for the most common European, American, British and Japanese I-shapes.