3-ply self-drilling screw connections for centre-sheathed steel shear walls

Abstract

Design provisions for the shear resistance of double shear (3-ply) cold-formed steel screw connections are not provided by the existing CSA S136 and AISI S100 Standards. The resistance of the mid-ply layer of screwed double shear connections was investigated to determine whether the use of the bolt bearing provisions was a reasonable substitute. Forty-eight individual normal ductility steel connections with fastener diameters between 4.17 mm and 5.49 mm and inner sheet thicknesses between 0.36 mm and 1.09 mm, as used for previously constructed centre-sheathed shear walls, were tested. Bearing damage and a combination of bearing and tearing failure were observed. The strengths of the connections tended to increase as displacement progressed due to expansion of the bearing area. When a displacement limit of 6.35 mm was enforced, the tested strengths of the screw connections were a reasonable match to the bolt bearing provisions. The resistance factor ϕ for the double shear screwed connections was identified to be 0.54 (LRFD) and 0.43 (LSD).