Fastener head pull-through resistance of plywood and oriented strand board

Abstract

A nailed or screwed sheathing-to-timber joint may fail in one of two possible modes when subjected to a load applied along the axis of the fastener: fastener head pull-through of the sheathing material and shank withdrawal from the timber. Currently, the Canadian timber design code does not provide specifications to check the first mode of failure. In this study, tests were conducted to determine the head pull-through strengths of some common hammer and power-driven nails and wood screws in plywood and in oriented strand board. These are compared with the calculated shank withdrawal strengths of the same fasteners from timber, assuming it to belong to the Douglas fir–larch species group. The test results show that there is no significant difference in strengths between plywood and oriented strand board. Head pull-through strength appears to increase with fastener diameter. The major conclusion reached is that, except for small size nails (less than 2 in. long), fastener head pull-through in sheathing prevails over shank withdrawal from timber in sheathing-to-timber joints when loaded axially.Key words: nail, wood screw, head pull-through, withdrawal strength, timber, design capacities.