The Behaviour of Sheathed Cold-Formed Steel Stud Wall Systems under In-plane and Out-of-plane Loading

Cold-formed steel (CFS) stud walls have been used extensively in the construction of low to medium-rise buildings, where they provide advantages of cost and material efficiency, offsite manufacturing, a panelized/modular approach and fast construction speeds. This study aims to develop a better understanding of the structural behaviour and performance of sheathed stud wall panels under in-plane and out-of-plane loadings considering the effects of key design parameters on the performance of these systems. To this end, detailed nonlinear finite element (FE) models of panel were developed to investigate the lateral behaviour of such systems by considering geometric imperfections and nonlinear material properties. The FE models, which were validated against available experimental data from the literature, were employed to conduct comprehensive parametric studies to assess the effects of key design variables, including screw spacing, thickness of Oriented Strand Board (OSB) and CFS members, board configuration, gravity load and single- and double-sheathed systems on the response of sheathed stud wall. The structural performance parameters and seismic characteristics of the studied panels were compared in terms of lateral load capacity, initial stiffness, failure mechanism, deformation capacity, ductility, and energy dissipation. Then, comprehensive experimental testing of sheathed CFS stud wall panels under out-of-plane loading was carried out to investigate the bending behaviour of the wall system by taking into account screw spacing, different material properties (i.e. thickness of OSB and CFS, and plywood), board scenarios and effects of main/auxiliary components. Based on the test results, the structural performance parameters (i.e. bending load capacity, maximum vertical deflection), failure mechanism, rotation of the C-shape studs and end-slips of the stud wall panels were determined for each parameter. In light of the analytical and experimental studies performed in this work, it was observed that the connection point for this type of composite structure plays an important role due to the fact that the capacity of sheathed CFS stud wall systems directly dependent on the behaviour of the fasteners. Therefore, small-scale specimens consisting of CFS stud members attached to wood-based boards were tested to characterise the behaviour of the load- slip response under push-out (shear), pull-out (tension) and rotational actions. The numerical and experimental key results of the work were summarised herein, aiming to provide a better understanding of the behaviour of fasteners and make data available for further analytical/numerical research.