Numerical simulation and design of steel equal-leg angle section beams

The stability and design of steel equal-leg angle section members subjected to uniaxial bending are studied herein. Numerical models are developed and validated against existing experimental data on steel equal-leg angle section beams. A numerical parametric study is then presented considering both hot-rolled and cold-formed steel angle section beams. Under major-axis bending, both lateral-torsional and local buckling are observed, with the former characterised by lateral deflection and twist of the cross-section along the member length but no cross-section deformation, while the latter by relative twist and transverse bending of the outstands. Under minor-axis bending, lateral-torsional buckling and Brazier flattening are observed, with the latter characterised by splaying of the outstands. When designing for major-axis bending according to Eurocode 3, both local and lateral-torsional buckling are considered; it is shown herein that equal-leg angle section beams under major-axis bending can be designed using a normalised slenderness based on the minimum of the local and lateral-torsional elastic buckling moments, while also considering the ratio of the local to the lateral-torsional elastic buckling moments. For minor-axis bending, Eurocode 3 only requires cross-section checks; this is found to result in unsafe predictions in some cases. It is shown that both safer and more accurate resistance predictions are achieved when account is taken both of lateral-torsional buckling and Brazier flattening in the design of equal-leg angle section beams under minor-axis bending using a normalised slenderness. Finally, new design proposals for steel equal-leg angle section beams are developed and verified against both physical experiments and numerical simulations. The proposed design rules are shown to offer substantially more accurate resistance predictions compared to existing codified design rules.