Mechanical properties of self-tapping screws and nails in wood

Abstract

This paper presents results of a research programme investigating the mechanical properties of self-tapping screws and nails in wood. The programme consisted of deformation-controlled tests to determine embedment strength, withdrawal strength, pull-through strength, bending capacity of individual screws, shear strength of screwed and nailed wood–wood connections, and shear strength of screwed wood–steel connections. All test specimens showed ductile behaviour. Based on the results from the first four types of tests, a simple calculation model for the shear strength of screwed wood–wood and wood–steel connections was set up and compared with test results from the last two types of tests. The calculation model took dowel action and friction (wood–wood and wood–steel) into account and showed excellent agreement with the test results.Key words: connections, screws, nails, shear strength, embedment strength, withdrawal strength, pull-through strength.