Behaviour and Design of Sheathed Cold-formed Steel Wall Studs subjected to Torsional Buckling

Abstract

The beauty of Cold-Formed Steel (CFS) is that it allows need based optimization owing to its ease in manufacturing the required structural sections. The superstructure in a light-gage steel construction is fabricated from CFS structural components of which wall panels forms a major part. The wall panels in the light-gage steel construction is attached to external sheathing on both sides of the panel. The inherent sheathing can brace the wall studs from buckling to some extent. However, there is lack of design guidelines to account the structural contribution of sheathing that offers resistance against global buckling of the CFS studs. Therefore, this dissertation focuses on investigating the effect of various sheathing board materials on CFS structural members. The recommendations of the current design specifications for the sheathing braced design of CFS wall studs is explained in detail. The experimental investigation was carried out for various design parameters such as sheathing configuration [sheathing material type, fastener spacing (df), and thickness of the sheathing (tb)] and different shapes (singly, point and doubly symmetric) and slenderness (local, distortional and global) of the CFS studs. The experimental results show that the sheathing can be appropriately designed to bear the forces developed at the sheathing-fastener connections. A comparison of experimental results and design predictions indicates that the current AISI design specifications is unconservative. The further investigation revealed that the sheathing stiffnesses predicted by AISI for the axial compression loading case has been implicitly recommended for both axial compression and out-of-plane loading case. Therefore, a new test setup is developed to simulate the failure of the CFS stud subjected to out-of-plane loading case and appropriate sheathing stiffness in determined