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

Abstract Based on 31 quasistatic tests and 27 constant-amplitudefatigue tests the withdrawal behaviour of a self-tapping timber screw under cyclic loading is examined in two configurations with regard 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 found where a larger penetration length yields inferior performance under cyclic loads. Further, in conjunction 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 obtained 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 a discussion of the state of knowledge regarding the relevant failure modes, the verification is reduced to the dominant failure modes withdrawal and steel tensile failure, while subsidiary effects such as bending in the fastener are inherentlyconsidered.