Fire resistance of novel concrete-steel-timber composite floor

Recently, an innovative flooring system has been developed that integrates the structural and performance benefits of concrete, light-gauge steel (LGS), and glulam panels. The system features a top-hat-shaped LGS section that is either nailed or glued to a glulam panel in a factory setting, depending on builder preference, forming a prefabricated permanent formwork. Once installed on-site, concrete is poured over the composite section, creating a tri-composite beam designed to enhance overall serviceability performance. This paper presents an experimental assessment of the fire behaviour of a full-scale steel–timber–concrete (CSTC) flooring system built by nail connections subjected to the AS 1530.4 standard furnace fire. A 4.0-metre CSTC beam under service loading conditions successfully resisted the standard fire exposure for nearly 100 min. Delamination of the glulam panel was observed, followed by a rapid increase in steel temperature and an associated reduction in load-carrying capacity. An analytical model based on the Gamma method from Appendix B of Eurocode 5 was developed and calibrated using experimental results, enabling the prediction of fire resistance levels (FRLs) for various glulam thicknesses and span lengths. Notably, the investigated CSTC system forms the basis of StrongFloor, a patented and commercialised flooring product that has already been implemented in real Australian building projects, including multiple schools in New South Wales and an office building, demonstrating its practical relevance beyond laboratory-scale development.