Analytical, experimental and numerical investigation on full-scale glulam trusses joined through birch plywood gusset plates

This study presents an analytical, experimental, and numerical investigation of full-scale glulam trusses connected through birch plywood gusset plates. Three trusses were joined through mechanical connectors, while three were adhesively bonded. Failure was designed to occur in the plywood plates subjected to a multi-axial stress state due to the convergence of three glulam elements in the node. The thickness of these plates varied between 9, 12 and 21 mm. This research aimed to evaluate the structural behaviour and failure mechanisms of birch plywood plates in timber connections. Experimental results showed that glued trusses generally exhibited larger ultimate loads and greater global stiffness compared to mechanically connected trusses. Nevertheless, the global stiffness was independent of the thickness of the central plywood plates. Analytical estimations for specimens that failed in the plywood generally showed good agreement with the experimental capacity despite a slight overestimation, which was attributed to the size effect of the plywood's mechanical properties. Glued trusses with thicker plywood plates (12 and 21 mm) exhibited failure in the glue line between the central plywood plate and the glulam member. Despite the size of the glued area being the same for these two trusses, the experimental capacity differed significantly due to the varying values of wood failure percentage in the glued connections that failed. Furthermore, 2D planar numerical models demonstrated good prediction of the global experimental stiffness for both glued and dowelled trusses. • Full-scale glulam trusses joined at the nodes using birch plywood gusset plates. • Connections with mechanical fasteners and adhesive bonding were tested and compared. • Analytical calculations and numerical simulations were compared to experiments. • The premature glue line failure with low wood failure percentage analysed and discussed.