Pull-out capacities of screw connections in thin steel battens exposed to bushfire conditions

Abstract

External building envelopes made of cold-formed steel (CFS) claddings are commonly used in bushfire prone areas due to their non-combustible properties. However, their designs should ensure safety under the combined action of enhanced wind suction loading and elevated temperatures experienced during bushfires. Although numerous studies have investigated the critical pull-out failures in CFS batten screw connections under wind suction loading at ambient temperature, the pull-out failure behaviour of batten screw connections under bushfire conditions has not been investigated. The main objective of this study is to examine the pull-out failure mechanisms and capacities of screw connections in CFS battens under wind suction loading at elevated temperatures. Two hundred and sixteen small-scale tests were conducted on CFS battens made of three commonly used thicknesses and both high (G550) and low (G300) strength steels. Tests were conducted at six different temperatures using three types of screw fasteners to investigate the critical localised pull-out failures of batten screw connections. The results of these tests were utilised to develop applicable design equations and capacity reduction factors for the pull-out capacities of batten screw connections under the combined action of wind suction loading and elevated temperatures. The findings of this study will help design and build structures safely in bushfire-prone regions.