Web crippling studies of cold-formed steel channel beams, experiments, numerical analyses and design rules

Cold-formed steel sections are increasingly used as floor joists, decks, wall studs and purlins in residential, industrial and commercial buildings, where they are often subjected to concentrated, localised loads or reactions. These concentrated forces acting on flexural members cause localised bearing failures. This bearing failure, commonly known as web crippling, is one of the critical failure modes of cold-formed steel members. Channel sections including unlipped channels, lipped channels and SupaCee sections that are unstiffened against this type of loading are vulnerable to web crippling failures.

This research has described a detailed investigation into the web crippling behaviour of cold-formed steel beams. This research has conducted comprehensive experimental studies using the new AISI S909 test procedures and associated numerical studies for three cold-formed steel channel sections subject to web crippling under End Two-Flange (ETF), Interior Two-Flange (ITF), End One-Flange (EOF) and Interior One-Flange (IOF) load cases. Improved design equations were derived within the currently used format (unified web crippling equation) for each channel section based on the results from both experimental and parametric studies conducted in this study under all four load cases. Direct strength method (DSM) based design equations were also developed based on the elastic buckling and yield load equations derived in this study for each channel section. Further, the effect of longitudinal stiffeners in SupaCee sections was also investigated.