TEST OF SCREW FASTENED PROFILED ROOFING SHEETS SUBJECT TO SIMULATED WIND UPLIFT

Screw fastened light gauge steel profiled roofing sheets are predomina ntly subjected to wind suction, i.e, wind uplift, and may fail locally in the vicinity of screw fasteners under strong or sustained fluctuat ing wind uplift. A series of static tests was performed on three types of profiled roofing sheets to investigate their structural behaviour and profile effects under simulated wind uplift. The considered sheeti ng profiles were arc-tangent, trapezoidal and ribbed, and an alternate (or equivalent alternate) sheeting crest fastening system was adopted . It was found that structural behaviour of the roofing sheets under u plift loads was greatly dependent on the sheeting profiles including t he shape and height of the crest. Both arc-tangent and trapezoidal typ e roofing sheets exhibited a large cross-sectional distortion stage an d a deflection hardening stage, following a local plastic collapse in the vicinity of the screw fasteners at the central support. The ribbed roofing sheet, however, had a final failure mode of sudden fracture w ith cracks under the screw fastener head at the central support. The u se of cyclone washers with screw fasteners reduced local plastic defor mations and, in general, increased initial failure loads of the roofin g sheets. Increasing the roofing span only slightly reduced the limit values of the reaction force per fastener at the central support due t o the local failure characteristic of the screw fastened profiled roof ing sheets.