Design for local buckling behaviour of welded high strength steel I-sections under bending

Local buckling behaviour of welded high strength steel (HSS) I-sections subjected to bending is crucial for structural designs, and has been found to be affected by the interactive effect between flanges and web. To realize accurate designs considering the local buckling behaviour, the continuous strength method (CSM), direct strength method (DSM) and the method from Kato, all of which incorporate the element interaction, have been developed for hot-rolled or cold-formed structures fabricated with conventional strength steel, aluminium or stainless steel. This paper aims to extend these methods for the design of welded HSS I-sections subject to bending. The results of 593 HSS material tensile tests and 40 tests on HSS I-beams are collated. 526 numerical models are generated to expand the data pool for this study using the validated finite element method. Underpinned by the collection of test data and numerical data generated from an extensive parametric study, the design expressions based on the CSM, DSM and the method from Kato, applicable to HSS I-sections under bending, are proposed. The statistical and reliability analysis indicate that the proposed CSM, DSM and Kato's method provide more satisfactory strength predictions than the codified design rules in Eurocode 3 and AISC specification. In comparison with the proposed CSM and DSM, the predictions based on the modified Kato's method show higher accuracy, which may be attributed to the separate consideration for the effect of flange and web slenderness in Kato's expression.