Past bushfire events have revealed that entire roof structures can be dislodged by bushfire‑enhanced winds before the fire front passes. Such loss of roof claddings exposes building structures to ember and flame attacks. Hence a series of large- and small-scale tests, supported by validated numerical models, were conducted to assess the critical pull-through and pull-out failures of cold-formed steel (CFS) roof and wall cladding systems under combined wind suction loading and elevated temperature exposure. For both crest- and valley-fixed claddings, pull-through capacity decreases with increasing temperature, while valley-fixed claddings achieved considerably higher capacities than crest-fixed systems.
Tests showed a splitting-type failure mode in one cladding system, which can permit ember entry during bushfires. This research has shown that suitable modifications to cladding geometry can eliminate this failure. It has also developed suitable pull-through capacity equations for crest- and valley-fixed CFS claddings under combined wind action and elevated temperature exposure.
This research also included pull-out failures of CFS claddings and battens and pull-through failures of battens, and with the improved understanding, suitable capacity equations were developed. Overall, these outcomes provide critical input for improving the current bushfire standards, supporting the use of safer, bushfire-resilient CFS cladding systems.
