Abstract
The cold‐formed steel (CFS) lipped channel section with circular holes has been widely used in low‐rise and multistory building structures as the column. However, the circular hole in the web makes the lipped channel column become susceptible to buckle. A total of 54 CFS lipped channel axial compression columns with and without circular holes were used to study the buckling behavior and the effective width design method. The interaction of the local buckling and the distortional buckling were observed for the short and intermediate columns, while the slender columns were controlled by the interaction of the local buckling, distortional buckling, and flexural buckling or flexural‐torsional buckling. The experimental failure loads were gradually decreased with the increase in the diameter of the circular hole for the specimens with the same section. The failure loads of the specimens with two holes were lower than those of the specimens with one hole with same section and same diameter of holes. Then, the experimental results were used to validate a nonlinear finite element model (FEM) previously developed by the authors. The validated FEM was subsequently used to obtain additional 36 numerical failure results concerning the effects of the length, the section, and the diameter and the number of the circular holes. Furthermore, the proposal to calculate the distortional buckling coefficient of the CFS lipped channel section with circular holes were put forward based on numerical analysis considering the reduction of effect of holes. Finally, a proposal to improve the effective width method (EWM) design approach for CFS lipped channel sections with circular holes under axial compression was presented. The comparisons between experimental and numerical capacities and their calculations provided by the proposed EWM design method illustrate a great application of the proposed approach.
Highlights
Introduction ecold-formed steel (CFS) lipped channel sections with holes in the web have been extensively used in low-rise and multistory building constructions as walls and floors
Guo and Yao [9] conducted the test of the intermediate CFS lipped channel columns with rectangular holes under axial compression and recommended a simplified effective width method (EWM)-based design method
Failure Modes. e failure modes of all 54 specimens are shown in Table 2, where L, D, F, and FT represent local buckling, distortional buckling, flexural buckling, and flexural-torsional, respectively. e failure modes listed in Table 1 indicates that the specimens with a length of 500 mm and 1000 mm were controlled by interaction of local buckling and distortional buckling, and the specimens with a length of 2000 mm failed with interaction of local buckling, distortional buckling, and overall buckling
Summary
54 CFS lipped channel columns including 42 columns with circular holes and 12 columns without hole were tested under axial compression. For each lipped channel section, three different nominal member lengths (500, 1000, and 2000 mm) were prepared. E average material properties obtained from the coupon tests including the 0.2% proof stress (f0.2), the elastic Young’s modulus (E), the ultimate tensile strength (fu), and the elongation after fracture (ε) were 602 N/mm2, 2.16 × 105 N/mm 615 N/mm, and 7.67%, respectively. A2 t b2 Figure 1: Section definition of CFS lipped channel columns with circular holes. E measured positions of strain gauges are depicted in Figures 8(c) and 8(d) for specimens with circular holes and without hole, respectively. A data acquisition system was used to automatically record the axial load, deformation, and strain of test specimens at regular intervals
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