Stiffeners for Enhanced Web Crippling Strength of Cold-Formed Steel Sections

The design efficiency of cold-formed steel (CFS) joists can be improved if the web crippling failure mode, which is a localized failure, can be shifted to a favorable mode of failure by increasing the web crippling capacity using stiffeners. The objective of this investigation is to establish appropriate stiffener arrangements for enhanced web crippling capacity of single web cold-formed lipped channel steel sections. The experimental investigation considered a total of 40 tests, subjected to interior two-flange (ITF), interior one-flange (IOF), end two-flange (ETF) and end one-flange (EOF) web crippling loads. The study also considered the impact of number of stiffeners and the number of screw fasteners. The first test series focused on single web elements subjected to ITF loading, where results showed that stiffened specimens gained about 25% in web crippling strength over corresponding unstiffened specimens. The same trend was found in IOF loading. The ETF tests had 106% increase in strength because the failure mode changed from web buckling to web yielding. The EOF tests had an increase in strength of 68% and failed due to web buckling. Based on these studies, it is concluded that the most effective and economical method to increase the web crippling strength would be to attach a single stiffener to the inside of the web using three screws.