In this paper, a two-node geometrically exact beam finite element developed by the author (Goncalves 2019), which is capable of accounting for Wagner effects, plasticity, geometric imperfections and residual stresses, is employed to assess the current Eurocode 3 (CEN 2005) provisions for I-section beams susceptible to lateral-torsional buckling and subjected to uniaxial or biaxial bending. For uniaxial bending, three support/loading cases are considered: (ⅰ) simply supported beams under uniform moment, (ⅱ) simply supported beams subjected to a mid-span vertical force and (ⅲ) cantilevers subjected to a free end vertical force. Besides I-sections with standard height-to-width ratios, wider flange sections are also considered and it is shown that the post-buckling behavior of the latter sections is quite different from that of the former ones, exhibiting an increase in the load carrying capacity which is not predicted by Eurocode 3. For biaxial bending, a standard I section is considered and three support/loading cases are examined: (ⅰ) simply supported beams under uniform moments, (ⅱ) beams simply supported at one end and fixed at the other, subjected to end moments, and (ⅲ) cantilevers subjected to free end forces. For these loadings, it is shown that the Eurocode 3 Method 2 interaction formulas can lead to very inaccurate estimates of the collapse load, either on the conservative or unconservative side.
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