Unified static-fatigue pull-through capacity equations for cold-formed steel roof battens

This paper investigates the fatigue pull-through capacity of cold-formed steel roof batten to rafter or truss connections based on static and constant amplitude cyclic tests. In order to represent all steel roof battens used worldwide, test battens were made using 0.75 and 0.95 mm G550 and 0.80 and 1.00 mm G300 cold-formed steel sheets. Each batten type was tested with 10 g and 12 g metal self-drilling screws that are commonly used to fasten steel roof battens to rafters or trusses. Tests were conducted using a small scale two-span batten test set-up as recommended by past research studies and simulated wind uplift loading on roof battens. Test results showed that cyclic wind uplift loading significantly reduced the pull-through capacities of steel roof battens, and thereby highlighted the need for accurate fatigue design rules. Therefore, a single-term exponential model was developed to determine the fatigue pull-through capacity reduction factors and was combined with the current static pull-through capacity equations to determine both static and fatigue pull-through capacities of steel roof battens subjected to wind uplift loading. The unified static-fatigue pull-through capacity equations were then verified using further constant amplitude cyclic tests of industrial steel roof battens. The proposed unified equations will facilitate effective designs of cold-formed steel roof battens without conducting the prototype Low-High-Low cyclic tests of roof assemblies.