Web crippling tests of cold-formed thin-walled built-up I-sections with web perforations

To investigate the web crippling behaviour and corresponding design formula for the mid-flange web crippling capacity of cold-formed steel (CFS) built-up I-sections with web perforations, forty built-up I-section specimens featuring web openings were first tested under localised loadings, covering the Interior-Two-Flange (ITF) and Interior loading (IL) cases. Test results indicate that the web height-to-thickness ratio h w / t and web-opening-height-to-web height ratio h h / h w exert pronounced influence on web crippling capacity. Finite-element simulations were performed using ABAQUS, and favorable agreement was obtained between numerical predictions and experimental measurements. The validated finite element model was further utilized to conduct parametric analyses, comprehensively exploring the effects of five key parameters on the local compressive performance of perforated built-up members, including the web hole height-to-web height ratio h h / h w , web height-to-thickness ratio h w / t , bearing width-to-web height ratio l b / h w , screw position ratio e / h w , and bend radius-to-thickness ratio r / t . Based on the experimental and numerical data, a calculation method is proposed for predicting the web-crippling capacity of perforated CFS built-up I-sections subjected to ITF and IL loading. Comparisons against experimental and finite-element results show that the proposed formula provides accurate predictions for the web-crippling capacity of CFS built-up I-sections with web perforations.