Experimental and analytical evaluation of shear capacity of reclaimed timber connections with thermo-mechanically densified wooden dowels

The reuse of reclaimed timber in structural applications is increasingly recognized as a strategy to extend material life cycles and reduce waste. Particular attention has recently turned to reusing reclaimed timber in adhesive-free laminated products with wooden dowels, where connection performance is critical. The aim of this study was to investigate the mechanical performance of double-shear connections assembled from reclaimed spruce timber using thermo-mechanically densified wooden dowels. The dowels were first evaluated in bending and embedment tests on lamellae made from both reclaimed and virgin spruce timber. The shear capacity of the connections was then evaluated in three layups: two homogeneous (all-reclaimed lamellae and all-virgin spruce lamellae) and one hybrid (reclaimed side lamellae with a central virgin spruce lamella). Analytical predictions were performed based on the draft of the new Eurocode 5, however, with two alternative definitions of dowel bending resistance (ultimate moment M u and yield moment M y ), and three alternative definitions of embedment strength ( f h 0.05 d calculated using the 0.05 d offset method, f h F max calculated from F max , and f h 0.8 F max calculated from 0.8 F max ). The three lamellae layups exhibited relatively similar mean capacities (7.3–8.3 kN). The all-reclaimed connections were on average 13 % stronger than the other assemblies, but this was not statistically significant. Among the model input variants, M u with f h 0.05 d showed the closest agreement with the experimental mean values, while M y with f h 0.05 d led to more conservative predictions preferable for design. In both cases, excluding outliers from the embedment test results reduced overestimation in the predictions. All other input variants overestimated the shear capacity. Overall, both homogeneous and hybrid connections with reclaimed timber lamellae performed comparably to virgin timber connections and exhibited predictable mechanical behavior. • Reclaimed timber connections delivered shear capacity equal to virgin spruce with strength class C24. • EYM predictions depend on how embedment strength and bending moment inputs are defined. • Excluding embedment strength outliers reduced overestimation in EYM predictions. • M u with f h 0.05 d as inputs led to the best match between mean values of EYM predictions and tests. • M y with f h 0.05 d gave the most conservative EYM predictions.