This paper presents an experimental and numerical investigation into the buckling behaviour of axially loaded cold-formed steel (CFS) zed and hat sections. In total, 12 experimental tests are reported, of those 6 tests are on CFS zed sections and the remaining 6 are on CFS hat sections. The failure modes, ultimate loads, and load–displacement curves of the specimens were reported and analyzed. The experiments revealed the deformation mechanism of both the zed and hat sections failing in distortional mode. Nonlinear finite element (FE) models are then described for both the zed and hat sections, which include material non-linearity and geometric imperfections. The validated finite element models were then used for the purpose of parametric studies comprising 140 models, which include 70 models each for CFS zed and hat sections. Ten different cross-sections were analyzed in the parametric study for both the zed and hat sections. The axial strengths obtained from the experimental tests and FE analysis were used to assess the performance of the current design guidelines as per the Direct Strength Method for both the zed and hat sections. From the comparison, it was found that the design strengths are un-conservative by 7% and 10% on average for CFS zed and hat sections, respectively. An improved design equation was therefore proposed for those CFS zed section columns, which failed by either distortional buckling or through a combination of distortional and global interactive buckling. The proposed equation gave a close comparison against FE results, being conservative to the FE results by only 3%. Reliability analysis was also performed to confirm the reliability of the proposed design equation.

本文对轴向加载的冷弯型钢 (CFS) zed 和 hat 截面的屈曲行为进行了实验和数值研究。总共报告了 12 个实验测试，其中 6 个测试在 CFS zed 部分，其余 6 个在 CFS hat 部分。报告并分析了试样的破坏模式、极限载荷和载荷-位移曲线。实验揭示了 zed 和 hat 截面在畸变模式下失败的变形机制。然后描述了 zed 和 hat 截面的非线性有限元 (FE) 模型，其中包括材料非线性和几何缺陷。然后将经过验证的有限元模型用于参数研究，包括 140 个模型，其中每个模型包括 70 个用于 CFS zed 和 hat 截面的模型。在 zed 和 hat 截面的参数研究中分析了十个不同的横截面。从实验测试和有限元分析中获得的轴向强度用于评估当前设计指南的性能，根据直接强度方法对 zed 和 hat 部分。从比较中发现，CFS zed 和帽子部分的设计强度分别平均不保守 7% 和 10%。因此，针对那些因扭曲屈曲或通过扭曲和全局交互屈曲的组合而失效的 CFS zed 截面柱提出了改进的设计方程。提出的方程与有限元结果进行了密切比较，仅比有限元结果保守了 3%。