Web crippling strength of perforated cold-formed ferritic stainless steel unlipped channels with restrained flanges under one-flange loadings

Abstract

Thin-walled stainless steel channels are becoming more widely used in the residential and commercial sectors because of their high corrosion resistance, especially in situations where low maintenance is required. However, there is a need also for web perforations for ease of installation of services; as a result such sections are susceptible to crippling in the web, particularly under concentrated loads applied near to the web perforations. This paper considers the use of perforated cold-formed ferritic stainless steel unlipped channels with restrained flanges subject to interior-one-flange and end-one-flange loadings, known as one-flange loadings. A total of 288 results are presented, comprising 18 laboratory and 270 numerical results. The numerical analysis in this paper uses nonlinear quasi-static finite element analysis with an implicit integration scheme. A comprehensive parametric study is described to determine web crippling strength reduction factors for different sizes of web perforations and cross-section dimensions. It is noted that no cold-formed stainless steel standard provides strength reduction factors for any one-flange loading. The strength reduction factors are first compared to reduction factors previously recommended for lipped cold-formed stainless steel channels. It is found that these existing equations are unreliable and unconservative for unlipped channels by as much as 20%. From both laboratory and finite element results, web crippling design equations are proposed for perforated channels under one-flange loadings; the proposed equations are shown to be reliable when compared against laboratory and numerical results.