Assessing the Bushfire Performance of Low-Rise Steel Structures Using Full Scale Bushfire Flame Front Simulation

Bushfire attack on buildings involves burning embers, radiant heat and/or direct flame impingement. Resistance to these attack mechanisms involves consideration of materials, design, installation and maintenance. Few solutions are currently available for construction in the most severe bushfire attack conditions, referred to in regulations as 'flame zone'. An experimental building incorporating steel sheet roofing and cladding together with steel roof, wall and floor framing was devised to withstand flame zone conditions. The test building was finished with a range of materials and features typical of low-rise construction, and built to six-star energy rating. Testing was carried out using a bushfire flame front simulator designed to recreate actual bushfire flame temperatures and radiant heat flux profiles. The simulator uses a liquid propane burner grid originally devised to assess the resistance of bushfire fighting vehicles caught directly in the path of a high-intensity bushfire. The test was conducted outdoors under prevailing wind conditions (within set criteria) allowing for the effects of oxygen supply and convective heat loss on test elements. Instrumentation measured air and building element surface temperatures throughout the building, radiation levels at the exposed building face and behind windows, and air quality inside the building. Post-test evaluation of the building was carried out to assess structural and building envelope weaknesses and repair needs.