Experimental Study of Adhesive and Metal-Free Laminated Timber Products Made of Uruguayan Pine

This study presents the experimental results of adhesive and metal-free laminated timber products made of Uruguayan pine. Dowel laminated timber (DLT) and wooden nail laminated timber (WNLT) were prepared using C22 pine lamellas and joined by wooden dowels or nails with diameters of 20 mm and 5.3 mm, respectively. For comparison, laminated timber products joined with 3.2 mm steel nails (NLT) were manufactured. Two nailing patterns, straight horizontal and zigzag, and three spacing between fasteners, 300, 250 and 150 mm were analysed. Shear tests on timber connections and four-point bending tests on structural size panels were performed, and the slip modulus and bending properties, respectively, were obtained. DLT connections showed significantly higher slip modulus values compared to WNLT and NLT connections. The bending stiffness (9.7 - 11.5 kN/mm2) and strength (35.4 – 57.4 N/mm2) of the DLT, WNLT and NLT panels did not show significant differences, suggesting that the connector material (wood or steel) and the diameter did not influence the load-carrying capacity of the panel. In general, the failure mode in the panels was in tension, probably attributed to pronounced fibre deviations and the presence of knots near the load application area. These findings suggest that adhesive and metal-free laminated timber products made of Uruguayan pine have structural properties that allow their use in residential floors, advancing towards more sustainable construction systems.