Bimoment Influence on the Design of Steel Elements According to the European Standards

Abstract In addition to axial forces and bending moments, the bimoment can significantly influence both the resistance and stability of steel members, independently of the geometry of their cross‐section. The complex interaction between the bimoment and other internal forces, and its implications for overall frame stability, remains an area of ongoing research. Despite numerous proposals by various Authors for interaction equations that account for these effects, the problem is not yet fully resolved, and current European standards often fail to adequately address this issue. Specifically, the old version of Eurocode 3 (EN1993‐1‐1:2005) did not comprehensively cover the influence of the bimoment on member stability. To cover this gap, the next generation of Eurocode 3 (EN1993‐1‐1:2022) introduces two new stability equations that account for the combined effects of all internal forces, including the bimoment. In the paper, after a recall on the Vlasov theorem, the ultimate load carrying capacity of selected isolated beam elements, experimentally and numerically evaluated has been compared with those derived from the application of the new EC3‐1‐1:2022 interaction equations. The selected cases demonstrated the importance of the new design rules for structural safety.