This paper introduces and verifies advanced three-dimensional finite element (FE) models for lightweight composite flooring systems composed of cold-formed steel (CFS) joists combined with structural plywood sheathing. The numerical models, developed in ANSYS, incorporate both material and geometric nonlinearities, simulate the load–slip response of mechanical fasteners, and include realistic contact definitions to capture the interaction between different components. The models were rigorously benchmarked against full-scale experimental tests, demonstrating strong agreement in terms of load–deflection behaviour, strain distribution along the section depth, and observed failure mechanisms. Building on this validation, extensive parametric analyses were performed to evaluate the impact of key design parameters, such as joist wall thickness, section depth, and the spacing of shear connectors. The findings confirm that increasing the thickness and depth of the steel joists enhances the flexural stiffness and load capacity of the flooring system, while closer fastener spacing improves composite action and overall structural efficiency. Finally, a simplified design example is provided to illustrate the proposed method for estimating bending resistance and serviceability deflection in such composite floors.

Cold-formed steel joists, timber floorboards, finite element modelling, composite floors, composite action, failure mode, ultimate load capacity