Locally reinforced timber joints with expanded tube fasteners

The study presented focuses on the development of a novel timber joint. Traditional timber joints with mechanical fasteners, particular dowel type fasteners, such as bolts exhibit a low strength and an unreliable stiffness and ductility caused by the presence of hole clearance and the unpredictable splitting of timber. The novel joint tackles all of these shortcomings. Local reinforcement glued to the timber members in the jointed area prevents unexpected splitting and results in the enhancement of the strength. By choosing a steel (gas) tube instead of a solid fastener, that fit in an over-sized hole, and by expanding the diameter after assembly of the joint, easy assembly and no hole clearance is insured. Due to the ductile behaviour of the reinforcement and the plastic deformation capacity of the tube the ductility of the joint is guaranteed. To assess the performance of this joints a comprehensive study was performed and reported in this article. Summarising the experimental results, it can be stated that densified veneer (ply)wood is an excellent mate.rial to reinforce the timber joint. It possesses a high embedding strength and stiffness compared to softwood and is able to sustain the high concentrated loads imposed by the tubes. It is demonstrated that the new joint possess a reliable and high strength and stiffness capacity in monotonic loading. When certain requirements are fulfilled the joint shows a superior behaviour in cyclic loading. Design examples show that when used in portal frames a considerable amount of timber can be saved, up to about 40%, compared to joints with traditional dowel type fasteners, without a loss of safety.Civil Engineering and Geoscience