Predicting the behaviour of external steel walls under bushfire radiant heat conditions

Abstract

External walls of the buildings possess the highest surface area and significantly contribute to the buildings’ bushfire resilience. Therefore, this study is aimed at advancing the understanding the behaviour of the external light steel framed walls exposed to bushfires, in particular the heat transfer across the walls. It presents a detailed numerical study where suitable numerical models were developed to simulate two series of experiments conducted under indoor and outdoor conditions and validated using the experimental results. The study was then extended to predict the heat transfer of light steel framed wall systems under different bushfire conditions for buildings in the bushfire flame zone (BAL-FZ) and the highest radiant heat exposure zone (BAL-40). The results showed (a) the importance of using steel cladding in the external walls, (b) the effect of different cavity insulation, and (c) the importance of selecting the suitable wall boards for different bushfire conditions. Based on the modelling results, it recommends suitable zone-specific wall systems to reduce cost and material use, and acceptable design load ratios for the construction of the selected external light steel framed walls in two critical regions in the bushland urban interface.