Reinforcing stop-splayed scarf joints with timber pegs: Role of slenderness

Repairing stop-splayed scarf-joints in beams or truss-rods is a frequent occurrence in restoring ancient timber structures. Reinforcement of carpentry joints by means of metallic elements as well as unconventional materials is extensively investigated in literature, while timber pegs in timber to timber connections are studied referring mainly to new timber structures. In the present paper, authors' previous research analysing the mechanical behaviour of stop-splayed scarf joints reinforced with timber pegs has been carried on, focusing on the evaluation of ductility which can be achieved by reinforcement with timber pegs. Moreover, the role of slenderness, the rate between jointed timber thickness and peg diameter is analysed. An experimental program has been carried out testing in axial tension two samples of fir scarf joints with an ash key: one sample constituted of two simple scarf joints, and one constituted of three scarf joints reinforced with two ash pegs of 20 mm of diameter. Comparing experimental results has allowed to better understand the role played by timber pegs in reinforcement and to evaluate the influence of reinforcement on ductility of reinforced scarf joints behaviour. Experimental results have also been compared with those obtained in a previous experimental study where an analogous experimental program has been made on smaller scarf joints reinforced with two ash pegs of 8 mm of diameter. So, the role played by slenderness has been focused. The evaluation of the attained results, even if not exhaustive for a reliable theoretical formulation of timber peg behaviour in reinforcing stop-splayed joints, has allowed the identification of some interesting features, that is stiffness and reinforcement due to timber pegs.