Evaluation of Shear Performance of Timber-Timber Composite Joints

The mechanical performance of timber composite floors is influenced by the degree of composite action between the components. In this study, the shear strength performance of cross-laminated timber and glued laminated timber composite floors based on the joining method was evaluated by push-out test. Eight types of timber-timber composite joints were evaluated using three different methods: lag screw joints, glued-in rod joints using fully threaded bolts and glass fiber reinforced plastic, and hybrid joints. Strength characteristics were derived to make theoretical predictions on the load-carrying capacity of the joints. The results showed that the glued-in rod joints were superior to the lag screw joints, with slip coefficients and ductility measured as 10 times and 2.5 times higher, respectively. The reliability of the strength characteristics of the glued-in rod joints was remarkably different depending on the presence or absence of anti-adhesive tape applied to the timber-to-timber joint surface. The load capacity of the hybrid joint, which combines mechanical and glued-in rod joining methods, was 47% higher than that of the lag screw joint and 38% higher than that of the glued-in bolt joint. In the European Yield Model modified to estimate the load capacity of joints, the rope effect and the yield moment of the fasteners had a remarkable impact on the predicted load capacity.