Web crippling of cold-formed high strength steel square and rectangular hollow sections under two-flange loading conditions

The web crippling behavior of cold-formed high strength steel (HSS) square and rectangular hollow sections under End-Two-Flange and Interior-Two-Flange loading conditions is studied. The cold-formed HSS tubular sections had nominal 0.2% proof stresses of 700 and 900 MPa. Finite element (FE) models were developed and validated against test results, showing the capability of replicating the experimental web crippling strengths, failure modes and load-deformation histories. Upon validation of the FE models, an extensive parametric study comprised 112 FE analyses was performed. The web crippling strengths obtained from the experimental and numerical investigations were compared with the nominal strengths calculated from the North American Specification, Australian/New Zealand Standard and European Code for cold-formed steel structures. The comparison results show that the nominal strengths predicted by the existing codified web crippling design provisions are either unconservative or overly conservative. Hence, new design rules are proposed for cold-formed HSS square and rectangular hollow sections by means of Direct Strength Method (DSM). It is shown that the modified DSM is able to provide reasonably good predictions.