Behavior of self-drilling screws in light-gauge steel construction

Single point, self-drilling fasteners are commonly used in light-gauge steel constructions including domestic, agricultural, and industrial structures. Fasteners installed in practice often suffer from a variety of in situ conditions that can affect the capacity of the fastener, such as construction tolerances creating combined shear and bending in the fastener (rather than pure shear), overtorqueing the fastener which can cause stripping of the thread or shearing off the head, nonperpendicular insertion of the fastener and accidental impact on the structure creating dynamic loads on the fastener. This note describes a series of 120 single lap connection tests of single screw fasteners under a variety of the above-mentioned conditions, performed on fasteners of different gauge inserted into different thicknesses and grades of steel. A design equation is proposed to modify the nominal shear strength to account for these conditions.