Mechanical behavior of V-shaped timber folded-plate structure joints reinforced with self-tapping screws

Timber folded-plate structures built with cross-laminated timber (CLT) panels can be applied to gymnasiums and conference halls. The design of the joints is crucial to facilitate the development of timber folded-plate structures. Considering that the compressive performance of CLT panels should be fully utilized and the failure of the joints was induced by the self-tapping screws, 45 degrees miter-connected (MCJR) and mortise-tenon (MTJR) joints reinforced with self-tapping screws were designed. Eight CLT specimen groups with varying connection type, loading direction, and self-tapping screw spacing and diameter were designed and subjected to tests. Typical characteristics of the failure modes and moment-rotation curves were evaluated, and the corresponding rotational stiffness, yield rotation, yield moment, ultimate rotation, and ultimate moment of the specimens were calculated. The results showed that the failure mode of the MCJR and MTJR in push was the pull-out of self-tapping screws, and those in pull included the shear-off and pull-out of self-tapping screws. The loading direction significantly influenced the rotational stiffness and ultimate moment of both types of joints. The mechanical behavior of the MTJR in pull was better than that of the MCJR in pull; however, the rotational stiffness and ultimate moment of the MTJR in push were relatively lower than those of the MCJR in push. Moreover, increased self-tapping screw diameter and decreased self-tapping screw spacing significantly improved the mechanical behavior of MCJR. Finally, an analytical model was established to determine the rotational stiffness of the MCJR and MTJR in different loading directions. A comparison of the analytical and experimental results demonstrates that the proposed analytical method can conservatively estimate the rotational stiffness of the MCJR and MTJR.