Tests and Finite Element Modelling of Cold-Formed Steel Zed and Hat Section Columns Under Axial Compression

摘要

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.