Modification of the Direct Strength Method for Assessing the Buckling Behavior of Cold-Formed Channel Purlins.

This paper evaluates and modifies the direct strength method (DSM) in AS/NZS 4600:2018 for cold- formed channel purlins based on the nonlinear analysis of Strand7 software. Initially, the original DSM curves from the THIN-WALL program are investigated for each buckling mode. Then the nonlinear analysis is performed using the finite element method (FEM). Next, the accuracy and reliability of the original and modified DSM curves are examined and analyzed based on the FEM results. In analyzing the results, the differences, mean and standard deviation between DSM and FEM results are compared. The percentage error ε is reasonable with the width-to-thickness ratios of 40 ≤ b/t ≤ 75, while in the distortional buckling mode, the acceptable range of the width-to-thickness ratio would be 32 ≤ b/t ≤ 63. Most sections have reasonable error values for different slenderness ratios λl (or λd). The results show that the modified DSM results are more accurate and reliable than the original ones, and the dispersion and calculation error of the test data will be smaller after the modification. However, the study's limitations would be the interference of the buckling modes and the sample size. The results of this research will provide structural engineers with a more comprehensive analysis of design methods and can be used as a reference for engineering design. [ABSTRACT FROM AUTHOR]