Mechanical properties of glulam moment-resisting joints reinforced by inclined self-tapping screws

Self-tapping screws (STS) are an effective fastener to enhance wooden moment-resisting joints. However, the effects of the arrangement and insertion angle of STS on the mechanical properties of wooden joints are less studied. Therefore, this study investigated the influence of these two factors on the mechanical properties of wooden joints by conducting cyclic loading tests using glulam moment-resisting joints reinforced by STS with different arrangements (round and square) and insertion angles (45° and 90°). The failure modes, bearing performances, and energy dissipation capacities were considered. The results showed that the insertion angle affected the bearing and energy dissipation capacity of the joints significantly, while the effect of arrangement was slight. The anti-rotation bending moments of the joints reinforced by inclined STS were higher by 31.7% and 13.5% when the arrangement of STS was circular and rectangular respectively compared with the joints reinforced by vertical STS under compression state, and were lower by 17.5 % and 22.9 % under tensile state. The restoring force characteristics of the joints were similar when the insertion angle of STS was the same. Furthermore, the joints had optimal ductility and stiffness when the arrangement was rectangular, and the insertion angle was 45°.