Web crippling capacity of fastened cold-formed steel channels with edge-stiffened web holes, un-stiffened web holes and plain webs under two-flange loading

Abstract

Cold-formed steel (CFS) channels with edge-stiffened web holes are widely used as flooring joists and bearers in industrial buildings and their flanges are fastened in most cases. This prevents the rotation of flanges and increases their web crippling capacity. In the literature, no information is available on the web crippling capacity of such fastened CFS channels with edge-stiffened web holes. This study presents the results of 36 new web crippling tests which were conducted on CFS channels with edge-stiffened web holes under fastened support subjected to two-flange loading. For comparison, specimens with no hole and un-stiffened web holes were also tested. Finite element (FE) models were then developed and validated against the experimental results. Using the validated FE models, an extensive parametric study involving 912 FE models was conducted. In the parametric study, web thickness, size of the web holes, length of bearing plate and length of edge-stiffener were varied. Test results indicated that the specimens with fastened flanges have higher ultimate capacity than those with unfastened flanges. For the case of fastened flanges, the web crippling capacity increased by 71% and 33% for the end-two-flange (ETF) and interior-two-flange (ITF) loading, respectively. Finally, the test results were compared with the design strengths predicted by the proposed equations of Uzzaman et al. (2020) for channels with web holes, and against the design equations of current design standards (American Iron and Steel Institute (AISI) (2016), Australian and New Zealand Standards (AS/NZS) (2018), and European Standard (EC3) (2006)) for plain channels. Upon comparison, it was found that the web crippling capacity reduction factor proposed by Uzzaman’s equations (2020) gave close predictions to the test results for CFS channels with edge-stiffened web holes.