Behaviour of normal and high-strength castellated steel beams

Abstract

This paper investigates the design and behaviour of normal- and high-strength castellated steel beams under distortional buckling. An efficient non-linear three-dimensional finite-element model has been developed for the analysis of the beams. The initial geometric imperfection, residual stresses and material non-linearities of flange and web portions of the steel beam sections were incorporated in the model. The non-linear finite-element model was verified against tests on castellated beams having different lengths and different cross-sections. An extensive parametric study was carried out to study the effects of the change in cross-section geometries, beam length, steel strength and lateral buckling restraints on the strength and distortional buckling behaviour of castellated steel beams. The study has shown that the use of high-strength steel offers a considerable increase in the failure loads of castellated beams, which has not been addressed to date in the literature. The failure loads predicted from the finite-element model were compared with that predicted from Australian Standards for steel beams under lateral buckling. It is shown that the Specification predictions are generally conservative for normal-strength castellated steel beams and quite conservative for high-strength castellated steel beams. Hence, a design equation was proposed for high-strength castellated steel beams.