Numerical studies and design of cold-formed steel battens subject to pull-through failures under bushfire conditions

Despite their common usage in bushfire zones due to their non-combustible properties, cold-formed steel claddings remain vulnerable to the combined effects of intense heat and strong wind actions typical of bushfires. These severe actions can trigger localised pull-through failures in thin-walled steel battens used between roof sheeting and roof trusses or rafters at their screw connections, compromising the integrity of entire roof cladding systems. While extensive research exists on the pull-through capacities of battens at ambient temperature, the impact of bushfire-enhanced wind action on these critical battens to rafter/truss connections remains poorly understood when exposed to elevated temperatures also. This study addresses the current research gaps through comprehensive finite element analyses of pull-through failures in cold-formed steel battens under combined wind suction loading and elevated temperatures. These analyses enabled an enhanced understanding of the pull-through failure behaviour, and highlighted the reductions in batten’s pull-through capacity at 500 °C. Validated by experimental results, the developed finite element models enabled a broad parametric study. Utilising the extensive pull-through capacity data, accurate design capacity equations were developed for the prediction of the pull-through capacity of cold-formed steel battens under bushfire conditions, promoting enhanced safety and resilience in bushfire-prone regions.