Out-of-plane (flatwise) behavior of through-tenon connections using the integral mechanical attachment technique

This paper aims to characterize the force–deformation response of through-tenon wood-wood connections subjected to out-of-plane (flatwise) loads. Six beech LVL timber specimen groups with variations in the fiber orientation (parallel and perpendicular) and tab insertion angle (45°, 60°, and 90°) are tested. Minimal replicate-to-replicate variability for each specimen group was observed. Overall, the specimens reached their maximum capacity soon after yielding. Furthermore, the joints are classified as having low ductility. For the specimens where the main fibers are oriented perpendicular to the loading direction, low strength and brittle failure were observed. The yield and maximum strengths and the slip modulus were not affected by the tab insertion angle and therefore remained almost constant among these specimens. For the specimens where the main fibers are oriented parallel to the loading direction, higher strength and more ductile behavior was observed. The following mechanisms contributed to the load-deformation response of these specimens: inter-fiber layer resistance, tension–compression, flexural, shear and torsional resistance of the fibers, and the embedment compression resistance. Furthermore, the damage propagation was not concentrated in a specific location/surface. The notch size was found to have a strong influence on the yield and maximum strengths, as well as the slip modulus of the 45°-angled specimens.