Buckling Resistance of Bolted Steel Angles–Numerical Study and Design Rules

Abstract Steel angle members bolted through one leg at their extremities are commonly met in lattice towers, where they are mainly used as bracings. Despite their practical relevance, their design relies on empirical expressions due to the incomplete understanding of their structural behaviour. This paper investigates the influence of the end joints on the buckling resistance of such members. A numerical model, validated against experimental results is employed for a parametric study to evaluate the impact on the ultimate buckling load of key parameters, including the size of the profile, the slenderness of the member and the number of the bolts at the end connections. The results highlight the significant influence of the number of the bolts, of the joint plasticity and the amplitude of imperfections on the buckling resistance. Comparisons with the predictions of the European normative standards for lattice towers, i.e. EN1993‐3‐1 and EN 50341‐1 as well as the new version prEN 1993‐3, reveal considerable discrepancies, with the normative predictions being both conservative and unsafe. The outcomes of the study highlight areas where existing standards may be insufficient and provide a basis for improving design recommendations to enhance safety and optimise material use.