Evaluation on the behaviour of screwed CFS joints subjected to combined loading

Abstract

Cold-formed steel (CFS) structures constructed by screw connections are commonly used in low-rise or mid-rise dwellings. Being a critical role affecting the strength and robustness of the structure, the configuration of joist-to-stud joints should be emphasized. However, the design method given by the existing specifications is incapable of covering screwed CFS joint with complex configuration. Therefore, further investigations are required for revealing the resistance and failure behaviour of CFS joist-to-stud screw joint under varying load modes. In this paper, laboratory tests of screw connections were conducted with the loading cases involving shear, tension, and combined tension and shear. This study concerns the behaviour of each connection in the elastic, plastic and failure stages. Finite element method (FEM) based on bushing connector elements was developed to simulate the performance of the screw connections in the physical experiment. Modelling details are given and a close correlation can be noticed when comparing numerical results against experimental outcomes. Moreover, a series of empirical design equations are proposed to predict the stiffness and resistance of the CFS joints.