An experimental investigation into span length effect in composite CFS and timber‐based flooring systems

Cold‐formed steel (CFS) panelised built‐offsite modern methods of construction offer economy of scale, high precision, reduction in construction waste and a more streamlined manufacturing and construction process, compared to traditional construction. Floors made with CFS joists and timber‐based flooring systems, often jointed using screws and structural adhesives, have become increasingly popular. Nevertheless, the beneficial effect of the timber flooring on overall floor structural behaviour is often ignored in design due to limited understanding of CFS joist‐timber board interaction and the effect of various influencing parameters. This article investigates, experimentally, the structural performance of such composite floors. This paper presents eighteen large scale bending tests of CFS composite floors and five pushout tests to investigate the effect of span length on composite action. The results demonstrate that a high degree of composite action can be achieved when both screws and adhesives are utilised, resulting in around 40% increase in flexural stiffness when compared to joist performance without boards. This can lead to a more efficient and sustainable design of CFS joisted floors. The results also show that further research is needed to extend existing design equations to cover short span lengths.