Strength and Ductility of Single Point, Self-Drilling Fasteners in Bending and Shear (No. R872)

Abstract

The report describes tests on connections featuring self-drilling screws and gaps between the connected parts. Gap typically occur when using inserts of a smaller dimension than the overlapping section, e.g. a tube. In such connections, the screws are subjected to the combined action of shear and bending. Tests were conducted on single and multiple screw connections loaded in shear. The gap was systematically increased from zero (pure shear) to about 1.3 times the screw diameter. Further gap-tests were conducted where the screw was inserted non-removed. These situations occur frequently in practice, particularly when access restrictions prevent perpendicular screw insertion or impede the control of the torque. Based on the tests, design equations are proposed for screw connections with gaps. A reliability analysis is included deriving an appropriate capacity factor for screw connections with gaps.