Experimental and numerical investigation of fixed-height cold-formed steel wall assemblies bearing on concrete slabs

Abstract

Cold-formed steel bearing walls are frequently installed on concrete slabs, which do not provide perfectly rigid and uniform conditions. However, existing design guidance assumes bearing condition has no impact on axial capacity, though cold-formed steel compressive members are particularly susceptible to these end conditions. Additionally, studs are typically installed at the edge of the concrete slab, which is prone to spalling and geometric irregularities, and stud walls are occasionally installed inadvertently overhanging from them. In this paper, the impact of non-uniform and partial bearing conditions on the axial strength of cold-formed steel (CFS) wall assemblies is identified and characterized experimentally and numerically. Studs of various cross-sections and bearing conditions were considered. Bearing conditions include: full bearing (edge distance ≥ 20.32 cm (8 inches)), close to the edge, at the edge, and partially overhanging from the slab. In addition to the experiments, high-fidelity finite element modeling of all the systems was conducted to validate the experimental results and elucidate the impact of parameters not captured during the tests. The results provide a means of evaluating existing design guidelines presented in the North American Specification of the American Iron and Steel Institute (AISI S100-16). Twenty-seven tests were conducted on CFS wall assemblies. They reveal that there is a potential need for improvement of current AISI specifications, where all bearing conditions are assumed rigid and uniform. Design recommendations for improving the current specification are discussed.