Reinforcing moment-resisting dowel-type timber connections: numerical and experimental investigation

A finite-element-based numerical modelling framework is proposed to simulate reinforced moment-resisting dowel-type timber connections and to directly estimate axial forces in fully-threaded screws. This study provides a rational basis for designing reinforcement in moment-resisting timber connections, using an efficient numerical model that captures load distribution among fasteners and axial forces in self-tapping screws under combined forces and bending moments. The framework integrates two scales of analysis. The complex nonlinear behaviour of the timber-fastener interaction is captured first in a detailed sub-model. Then, this local response is scaled up to the multiple-fastener level to predict the connection’s global response. Fully-threaded screws are modelled as truss elements kinematically coupled to the timber’s finite element mesh at the multiple-fastener level. The model is used to design reinforcements for selected configurations, which are subsequently experimentally tested under combined shear and bending. Reference tests without reinforcement are also conducted for comparison, varying the number of fasteners and the slenderness ratio. Results confirm the numerical model’s accuracy in predicting the connection’s ductile response, the reinforcement’s axial forces, and the significant increase in load-carrying capacity and ductility observed in the reinforced tests. Furthermore, experimental results show that reinforcing with fully-threaded screws is more effective than increasing the number of fasteners or their slenderness ratio.