Abstract
The use of cold-formed steel (CFS) channels with circular or rectangular web holes is becoming increasingly popular in building structures. However, such holes can result in sections becoming more susceptible to buckle and display lower load-carrying capacities. This paper presents a total of 42 axial compression tests of CFS lipped channel slender columns with and without circular and rectangular web holes, including different hole sizes and cross sections. The test results show that the axial members with a small ratio of width to thickness were governed by global buckling, while the members with a large ratio of width to thickness were controlled by the interaction of local, distortional, and global buckling. The axial strength decreased maximum by 20.48% and 22.98% for the member with circular holes and rectangular holes, compared to a member without a web hole. Then, a nonlinear elastoplastic finite element model (FEM) was developed, and the analysis results showed good agreement with the test results. The validated FE model was used to conduct a parametric study involving 36 FEMs to investigate the effects of column slenderness, dimension of the hole, and the number of holes on the axial strength of such channels. Furthermore, the formulas to predict the global buckling coefficient and the effective area were modified for such sections with holes by using the verified FEM. Finally, the tests and parametric study results were compared against the design strengths calculated in accordance with the developed method. The comparison results show that the proposed design method closely predicts the axial capacity of CFS channels with circular or rectangular web holes.
Highlights
Introduction ecold-formed steel (CFS) lipped channel sections have been widely used in buildings as walls, floors, and ceilings due to their highstrength-to-weight ratio and ease of construction
Stub column tests conducted by Colberg [1] indicated that the load-carrying capacity decreased with the increasing of the ratio of circular hole diameter-to-depth of the web. e same conclusions have been reported for stub columns with circular, rectangular, and slotted web holes [2, 3]. e compression tests of 24 short and intermediate CFS lipped channel columns with and without slotted web holes showed that the presence of slotted holes caused a slight decrease in the ultimate capacity [4]. e axially compressed tests of intermediate length CFS lipped channel columns with circular holes indicated that the stress of the plate adjacent to the circular hole was higher than that of other parts and the plate adjacent to the circle hole yielded early [5]
For lipped channel columns with web stiffener, numerical and experimental studies were carried out to analyze the effects of holes on the failure mode and load-carrying capacity by Yao et al [5]. e results demonstrated that the holes led to the change of bucking mode and decreased the ultimate
Summary
Initial geometric imperfections along the longitudinal direction of all specimens were measured before tests. E initial geometric imperfections were measured with an interval of 150 mm along the specimen length. E initial geometric imperfections along the longitudinal direction for specimens C7510-NH-1, C7508-CH3-1, C8008-NH-1, and C9008-NH1 are illustrated in Figures 5(a)–5(d), respectively. Four-position transducers (Figure 7(a)) and four strain gauges (Figure 7(b)) were arranged at the mid-height of the column and a position transducer is arranged at the upper end plate of the specimen to measure the vertical displacement under load. Four-position transducers (Figure 7(e)) were arranged at the middle location to measure the displacement of web adjacent to the hole and flanges. All the test data could be obtained by using the YJ16 data acquisition instrument
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