Rebars as alternatives for smooth dowels in timber connections: An experimental, analytical and numerical study

This study investigates the possibility of utilizing steel rebars as alternative mechanical fasteners in timber structures. Adopting rebars rather than conventional smooth dowels as fasteners in timber-timber connections might have positive aspects in terms of environmental impact and structural capacity. As to the environmental aspect, it should be mentioned that rebars are typically from two primary sources, namely: a) reused rebar offcuts or b) recycled steel scraps. Regardless of different origins, rebars have reduced environmental impact, especially since rebar offcuts are the primary waste source in concrete construction. As to the strength aspect, which is the main focus of this paper, the authors aimed to check whether enhanced load capacity of dowel-type connections could be achieved due to the higher withdrawal capacity of rebars as compared to smooth dowels. To verify this, tension-shear specimens with either two or four shear planes, adopting smooth dowels or steel rebars as the mechanical fasteners, were experimentally investigated. Plywood with thicknesses of 15 mm or 21 mm was adopted to further verify the contribution from the friction, assuming that thicker plywood generates a higher withdrawal capacity. Analytical models in Eurocode 5 were also adopted to predict the shear plane capacity and the connection stiffness during loading phases. Thereafter, a numerical model was constructed to verify the structural benefits of rebars by adopting different friction models. The model aims to explain experimental observations both quantitively and qualitatively. • Timber connections with rebars depict higher shear capacity than smooth dowels. • The hardening effect from the rebar ribs’ friction contributes to extra capacities. • Rebar ribs’ contribution to capacity verified by plywood with different thicknesses. • Eurocode 5 formulas underestimate joint capacity but overestimate stiffness values. • The numerical models verify rebars’ structural merits via different friction models.