Flexural Behaviour and Design of Cold-Formed Steel Wall Panels Sheathed with Particle Cement Board

Abstract

The bracing effect of Particle Cement Board (PCB) sheathing for the Cold-formed steel (CFS) wall stud is explored in this study. Owing to the higher slenderness, the CFS wall stud requires additional bracing to inhibit the instability failures such as flexural and lateral torsional buckling. Twenty sheathed CFS wall studs were tested to investigate the structural effect of PCB sheathing under out-of-plane loading. The key design factors such as sheathing arrangements (screw spacing and sheathing thickness) and slenderness of the CFS studs were examined. The experimental results indicated that the CFS studs with vulnerability to fail in both local buckling (fcrl <<fy) and LTB (fcre <<fy) can be effectively braced by particle cement board sheathing. The experimental results, together with the failure modes of the sheathed CFS studs were compared with the predicted strengths using the latest sheathing braced design rules. The critical elastic buckling stresses corresponding to different failure modes for the direct strength method (DSM) of CFS structural member design were determined using the latest modified rule. The latest sheathing braced design rules accurately predicted the failure modes of the PCB sheathed CFS stud. However, the design moment capacities predicted by the latest sheathing braced design rules are overly conservative compared to the experimental moment capacities. The reasons pertaining to the over conservative design predictions are discussed. A set of preliminary suggestions to effectively codify the design rules for the CFS wall panels are given.