Local-distortional interactive behavior and design of cold-formed steel C-sections with & without slotted holes

Cold-formed thin-walled steel structures are widely utilized owing to their significant performance in energy saving, environmental protection, and efficient utilization. The thin-walled nature of the sections is prone to complicated structural instability behavior. This study aims to investigate the ultimate load-carrying capacity of cold-formed steel (CFS) columns with holes in the web under local-distortional interaction through experiments. Thirty-two axial compression tests were conducted on fixed-end lipped channel columns with and without slotted holes. The test results, including the failure behavior, load-displacement curves, and load-strain curves of the specimens, demonstrated that local-distortional interaction occurred. Moreover, the ulti-mate strengths of the specimens with and without holes were compared to explore the effect of slotted holes. The results show that the slotted holes provide a slightly detrimental influence on the load-carrying capacity and stiffness. Finally, the current Direct Strength Method (DSM) to predict the actual L-D interaction behavior of lipped channel columns (with and without slotted holes) was evaluated based on the test results. It was shown that the current DSM cannot accu-rately predict the load-carrying capacity of CFS perforated columns with small lip stiffener widths. Besides, the novel design criterion with the DSM-shaped expressions to identify the actual L-D interaction behavior was discussed, and an improved method was proposed for perforated specimens.