Mechanical performance of timber connection made by wood welding technique

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University of New Brunswick


A new type of timber connection is developed using the wood friction welding technique, which is a non-adhesive gluing process. During this process, heat is needed to melt the wood material in the course of pressing one wood piece to another via linear vibration or rotation. The objective of this study was to investigate the mechanical performance of timber connections made via the rotation welding. The spruce-pine-fir (S-P-F) lumber was used to fabricate the members, and the sugar maple (Acer saccharum) was used to make the dowels with a diameter of 19mm (3/4"). The bolts were used to make the timber connections as well as for comparison purpose. Two loading directions (parallel (PA) and perpendicular (PE)) and three connection types (push-in dowel (P), welding dowel (W), and bolted (B)), were considered in the design of experiment. There were two (2) groups of three (3) sets each. Each set had six (6) replicates, making a total of 36 specimens. Each joint specimen was performed on a universal mechanical testing machine. It was found that (1) The peak load and initial stiffness of set PA-B were 33kN and 5kN/mm, which were about 135% larger than and 45% less than set PA-W. The peak load and initial stiffness of set PA-P were 14% and 50% larger than that of set PA-W. (2) The yield loads for sets PA-P and PA-W were almost the same, being 13kN, which were about 150% lower than that of set PA-B. (3) The ductility and energy accumulated of set PA-B were about 30% less than and 140% larger than set PA-W. (4) The average peak load and initial stiffness of group PA were about 25% and 27% greater than those of group PE.(5) Johansen Theory was found to be conservative in derivation of engineering design values of wood dowelled and metal bolted joints. (6) The failure of wood doweled joint specimens was the fracture of the dowels, and the failure of bolted joint specimens was the crushing of member wood. (7) The mechanical properties of welded joints were similar to those of push-in joints. (8) The welding process did not generate cracks, minimizing stress concentrations, in wood members, in comparison to push-in process. It has great potential in fabrication of dowel-laminated wood products and repair/reinforcement of laminated beams. As for the future work, application of welding techniques should be explored during the manufacturing and construction of timber products and buildings, such as reinforcing glued laminated wood with notches. Key words: wood welding, timber joints, peak load, initial stiffness, yield load, ductility, energy dissipation, European Yield Model.