Structural behaviour and capacity of cold-formed steel channel sections with elongated edge-stiffened and unstiffened web holes under compression

Over the past decade, cold-formed steel (CFS) channel sections with edge-stiffened circular web holes have been developed and are now widely used in New Zealand. Previous studies on axial compression have demonstrated enhanced axial capacity when utilizing edge-stiffened web holes in these channel sections. Building on this, research has extended to include elongated web holes, but literature lacks investigations into the axial capacity of CFS channel sections with elongated edge-stiffened web holes (EEH). This study addresses this gap. Non-linear finite element (FE) analysis was employed to examine the axial capacity of CFS channel sections with both EEH and elongated unstiffened web holes (EUH). FE models were developed and validated against the experimental results available in the literature. Using the validated FE models, a comprehensive parametric study comprising 990 finite element analysis (FEA) results was conducted. These parametric study results were compared with design strengths calculated from the current design guidelines of the American Iron and Steel Institute (AISI 2016) and Australia/New Zealand Standards (AS/NZS 2018) for CFS channel sections with plain webs and EUH. Also, design equations in the form of capacity reduction and enhancement factors for effective width method (EWM) and modified direct strength method (DSM) equations were proposed to determine the axial capacity of CFS channel sections with EEH and EUH. Finally, a reliability analysis was performed, demonstrating that the proposed equations are reliable and can provide accurate predictions for the axial capacity of such sections.