Experimental and numerical investigations of LSF walls subject to distortional buckling

Light gauge Steel Frame (LSF) wall systems are increasingly replacing the conventional concrete and heavy steel structural systems due to the many advantages they offer. Web stiffeners are often included in the wall stud sections to improve their local buckling capacities and thus most of these studs are prone to buckle distortionally. Unlike for other buckling modes, the composite behaviour of wall studs sheathed with gypsum plasterboard is complicated for distortional buckling. This paper presents the details and results of experimental and numerical investigations into the structural behaviour of LSF walls subject to distortional buckling. Eight LSF wall assemblies were tested with varying parameters such as stud geometry, plasterboard thickness, number of plasterboard layers, sheathing arrangements and screw spacing. A high-fidelity finite element model capable of simulating the behaviour of LSF walls was developed and validated using the experimental results. The developed numerical models included geometric and material nonlinearities, initial geometric imperfections, contact interactions between stud, track and plasterboard sheathing, and most importantly the non-linear in-plane and pull-through screw connection behaviour. The validated numerical model was also used to further investigate the distortional buckling behaviour of LSF walls and the effects of some of the key modelling parameters. The analyses showed that stud-to-sheathing screw connections have a significant effect on the load-bearing capacity of LSF walls subject to distortional buckling, which can be enhanced by reducing the screw spacing and increasing the sheathing thickness and the number of sheathing layers.