Estimation of the high-cycle fatigue behaviour of timber connections with inclined screws under tension

Abstract

On the basis of 31 quasistatic and 27 constant-amplitude fatigue tests, the withdrawal behaviour of a self-tapping timber screw under cyclic loading is examined in two configurations with respect to the penetration length. Together with similar results from earlier withdrawal tests on threaded rods, indications of a dependence of the bearable load cycles on the penetration length are revealed. A larger penetration length was found to yield inferior performance under cyclic loads. Furthermore, combined with results from earlier axial tensile tests on the examined screw, insights into the transition point between steel tensile failure and withdrawal are gained. The results on the withdrawal failure mode are combined with results from earlier studies to develop a proposal for a holistic verification concept for the high-cycle fatigue design of connections with inclined self-tapping screws. After reviewing the relevant failure modes, the verification is reduced to the dominant failure modes, namely, withdrawal and steel tensile failure. Subsidiary effects such as bending in the fastener are inherently considered.