Search

To propose a design method for determining and designing cold-formed steel (CFS) U-section columns with the local and global (LG) interactive buckling, an experimental investigation and numerical simulation with pin-ended columns were carried out in this study. A total of 12 specimens were investigated, considering four cross-section dimensions. In addition, a finite element model (FEM) was established to simulate experimental specimens, the results of which were compared with those of the experiment. Furthermore, the width-to-height ratio, the key parameter effecting the buckling modes and ultimate capacity of CFS U-section columns, was analyzed in detail using a numerical simulation. Finally, based on the experimental and numerical results, an approach for calculating the ultimate capacity of CFS U-section columns was proposed. The accuracy and applicability of the proposed method were verified by the extensive experimental and finite element data. The results indicate that the design method can accurately predict the ultimate strength of CFS U-section columns with the LG interactive buckling.

The effect of membrane stress on axial strength of screw composite thin plate is addressed in this paper. In order to study the post-buckling behavior of the screw composite thin plate, the instability mechanism was analyzed theoretically based on the large deflection theory, experimental and numerical investigation were described in this paper. Considering the shear deformation and screw restraint, the calculation model of ultimate stress for the screw composite thin plate was established, and the analytical formula of the ultimate stress of the screw composite thin plate with four simply supported edges and two opposite sides under uniform compression was derived. The composite thin plate obtained from cold-formed steel back-to-back built-up short columns assembled by self-drilling screws, commonly used in practical projects, was used as the test models. Then, the experimental and numerical results were compared with theoretical results mentioned above to modify the proposed formula. According to the comparison, the modified coefficient φ was derived by nonlinear regression, and the modified ultimate stresses were in good agreement with the experimental and numerical results, the results were reasonable and reliable.

This paper reports an experimental and theoretical investigation of gypsum-filled cold-formed steel (CFS) shear walls, for the purpose of addressing the estimation of lateral stiffness. A series of gypsum-filled CFS shear walls were tested under reversed cyclic loading. The infill walls declare the limit states in the failure of screw connections as well as the compressive failure of gypsum fillings. Besides, the shear performance of screw connections between CFS profiles and sheathings were also investigated by the local tests. The contributions of lateral stiffness under shear force mainly include the sheathings as stressed skins and the infill gypsum as bracing bars. A theoretical prediction of lateral stiffness for CFS infill walls was proposed based on superposition methods, which has a good agreement with the wall tests. Moreover, the shear stiffness of screw connections is required to determine the contribution of sheathings to lateral stiffness. Considering the extrusion deformation of sheathings along with the bending deformation of CFS profiles caused by the tilt of screws, a theoretical method was recommended to estimate the shear stiffness of screw connections.

Cold formed steel (CFS) built-up members are increasingly used in buildings because of their better mechanical performance. In this paper, the elastic buckling behaviors of the composite plates extracted from CFS back-to-back built-up columns were investigated using a combination of tests and finite element (FE) analyses. A total of 18 CFS back-to-back built-up columns were tested in this study. The built-up sections were fabricated from two identical C-section components and were assembled with self-drilling screws at their webs. The effects of screw number and screw spacing on the critical buckling loads and buckling modes of the built-up column were investigated in this paper. Moreover, extensive parametric studies were conducted in detail by developing CFS FE models based on the validation process with available experimental results. In addition, both the critical buckling loads as well as the buckling modes predicted from the FE analyses were in good agreement with the laboratory test results.