Numerical modeling of external light gauge steel framed wall systems exposed to bushfire flame zone conditions

Bushfire-related building losses cause adverse economic impacts to countries prone to bushfires. Building materials and components play a vital role in reducing these impacts. However, due to high costs of experimental studies and lack of numerical studies, the heat transfer behavior of building’s external components in bushfire-prone areas has not been adequately investigated. Often large-scale heat transfer models are developed using Computational Fluid Dynamics (CFD) tools, and the availability of CFD models for heat transfer in building components improves the understanding of the behavior of systems and systems of systems. Therefore, this paper uses a numerical modeling approach to investigate the bushfire/wildfire resistance of external Light gauge Steel Framed (LSF) wall systems. Both full-scale and small-scale heat transfer models were developed for the LSF wall systems. Experimental results of six internal and external LSF wall systems with varying plasterboard thickness and cladding material were used to validate the developed models. The study was then extended to investigate the bushfire resistance of seven external wall systems under two different bushfire flame zone conditions. The results illustrate the significant effects of fire curves, LSF wall components and configuration on the heat transfer across the walls. They have shown 1) the favorable performance of steel cladding and Autoclaved Aerated Concrete (AAC) panels when used on the external side of wall systems and 2) the adequacy of thin-walled steel studs’ load-bearing capacity during bushfire exposures. This study has shown that most of the investigated external LSF walls could be reused with cost-effective retrofitting such as replacing the Fire Side (FS) steel cladding after bushfire exposures. Overall, this study has advanced the understanding of the behavior of external light steel framed walls under bushfire flame zone conditions.