Numerical modelling of light gauge steel framed floors under standard fire conditions

The performance of light gauge steel framed (LSF) floors under fire conditions is primarily determined by plasterboard fall-off and subsequent heat ingress. Due to the high costs and time demands of full-scale fire tests, there is a critical need for numerical models capable of predicting the behaviour and fire resistance levels (FRLs) of LSF floors. However, the complexity of modelling plasterboard fall-off has hindered the development of such models. This study presents suitable advanced finite element (FE) heat transfer models that can predict the temperature-time profiles by including plasterboard fall-off, which are verified against standard fire test results. Additionally, new structural FE models incorporating sheathing have been developed to capture the influence of sheathing on the behaviour of LSF floors under both ambient and fire conditions. Overcoming the computational challenges associated with elevated temperatures was essential to the successful development of these structural FE models. By using the sequentially coupled heat transfer and structural FE models, the effect of different flooring materials (plywood and fibre cement panel) on FRL was investigated. Results indicate negligible FRL differences between these flooring options. A parametric study was also conducted to determine the FRLs of commonly used LSF floor configurations under varying load ratios. The developed models offer a robust tool for comprehensive parametric investigations to establish the FRL data for LSF floor systems, eliminating the need for extensive full-scale fire testing. • Developed heat transfer and structural FE models to predict the behaviour of full-scale LSF floors under fire conditions. • Sheathed single-joist models simulated the response of full-scale LSF floors well under both ambient and fire conditions. • Heat transfer models incorporating plasterboard fall-off effectively predicted LSF floor temperatures. • Sequentially coupled heat transfer and structural FE models offer a cost-effective alternative to full-scale fire tests. • Parametric studies indicated that flooring has minimal impact on the FRL of LSF floor systems.