General formulation for uniform and non‐uniform high‐strength steel slender I‐section beams

The Ayrton–Perry approach is the basis of Eurocode 3 rules for buckling resistance, with distinct curves and imperfection factors depending on section type, steel grade, and other parameters. For generic members – built‐up or not, uniform or not, with complex supports or not – the code allows either the general method (clause 8.3.4 of Eurocode 3) or advanced numerical simulations. Yet, the general method shows wide scatter and often underestimates resistance, while numerical analyses are time‐consuming and strongly user‐dependent. To overcome these limitations, the general formulation was introduced by Tankova et al. (2018) for members with variable geometry, loads, and supports and recently extended to mono‐symmetric I‐beams. However, it has only been validated for Class 1 and 2 sections, not for Class 4. This paper extends the general formulation to uniform and non‐uniform slender I‐section beams subjected to arbitrary loads, boundary conditions, and partial lateral restraints. An advanced numerical model, calibrated against experimental data, was employed to conduct a comprehensive parametric study considering different cross‐sections, a range of normalized slenderness values, S460 and S690 steel grades, and different load applications. The proposal was compared with the numerical results, demonstrating a safe‐sided and well‐calibrated solution for the buckling resistance of high‐strength steel slender I‐section beams.