Wood joints and laminated wood beams assembled by mechanically-welded wood dowels

Dowel welding by high-speed rotation was used to join two wood blocks and strong joints were obtained. Dowel angle to the surface of the wood blocks to be joined had a marked influence on the mechanical performance of the joint. When the dowel was inserted at 90 degrees to the substrate, the dowel was subjected to and resisted a shear force only. When introduced at an angle such as 30 degrees or 45 degrees, the dowel was subjected to and resisted both shear and tension forces, resulting in better joint strength. The joint almost always failed by dowel fracture. The dowel/substrate interface was almost always stronger and did not break. Short two-layer beams joined exclusively by a series of welded dowels were prepared, tested in shear according to structural standards, and their performance was compared to those of solid wood and of glued laminated beams (glulam) of the same dimensions. The short two-layer beams prepared for testing met the Eurocode 5 standard requirements when the optimum dowel insertion angle was used. Then 2-m-long two-layer wood beams were prepared, with the two layers connected exclusively by a series of welded dowels, and tested in bending. Their maximum failure strength and stiffness in bending were determined. These beams outperformed both nailed beams and glued-dowel beams. All the beams had the same length and conformation. The number of nails necessary was double the number of dowels used.