Behaviour of cold-formed steel built-up I-sections with perforated web under localized forces

This research focused on the web crippling behaviour of cold-formed steel (CFS) built-up I-sections with perforated web. The built-up I-sections were made up of two equal-sized unlipped channels fastened back-to-back in the web. The web hole was situated at the middle height of the web and directly under the bearing plate. Firstly, an experimental program consisting of 13 specimens without web holes and 38 specimens with perforated web is described. The built-up I-section members were tested under four different loading cases, including End-Two-Flange (ETF), Interior-Two-Flange (ITF), End loading (EL) and Interior loading (IL). Numerical simulation was conducted after the tests. The experimental results were utilized in the development and validation of nonlinear finite element (FE) models. Then the verified FE models were utilized to perform a parametric investigation of 318 built-up I-sections. The numerical and experimental strengths for specimens without web holes were compared to the design predictions from the existing design standards. The findings show that the strengths calculated from the existing standards are either conservative or unconservative. It should be mentioned that the existing international design standards do not have explicit design formula to predict the strengths of CFS built-up I-sections with perforated web undergoing web crippling. As a result, the test and FE capacities of specimens with perforated web were compared to the capacities predicted from the strength reduction factor formulas derived in this study. It is shown that the newly developed formulas can accurately calculate the web crippling capacities of CFS built-up I-sections with perforated web.