An analytical procedure for failure and stiffness prediction of glued-in rod timber connections

Glued-in rod (GiR) timber joints, featuring a composition of a rod, adhesive (glue), and timber, play a pivotal role within the mass timber construction industry where the performance of the GiR connections is imperative for the success of massive timber-based structural systems. However, the intricate mechanical complexities inherent in the load-displacement behaviour of the timber/adhesive joints present significant challenges in the accurate analysis and design of the GiR connections. This article endeavours to use the theory of elasticity and fracture mechanics to derive an analytical procedure for assessing the stiffness and loading capacity of the single GiR joints subjected to pull-pull, pull-push, rod-pull, and wood-pull loading configurations. In the proposed analytical model, the adherents are treated as isotropic, orthotropic, or multilayer composite materials. Given the intricate anisotropic nature of the timber and the composition of the GiR connections, a judicious combination of failure criteria inspired by continuum damage mechanics or fracture mechanics is adopted, to effectively capture the peak load associated with a wide range of failure modes. The accuracy of the proposed analytical model is evaluated through comparison with the laboratory test data, Volkersen's theory, and EN1995-1-1 models, providing insights for efficient analysis and design of timber connections with GiR.