Local and global ductility relationships of timber moment-resisting frames with dowel-type connections

Timber moment-resisting frames (TMRFs) with semi-rigid beam-to-column connections are favoured in mass timber construction due to their architectural flexibility. This study develops analytical relationships that link the ductility of dowel-type beam-to-column connections to the global ductility of TMRFs. The formulations are derived by modelling the connections as nonlinear rotational springs, allowing global ductility to be expressed as a function of connection ductility and rotational stiffness at different limit states. Two connection types from previous experimental studies, tight-fit pin dowels and bolted connections, are considered, and the proposed equations are verified using several archetypes with different configurations. The results show that frames with pin dowel connections achieve higher system ductility than those with bolted connections. The analytical predictions align well with nonlinear static analysis results for low-rise frames and remain conservative for higher-rise cases. Nonlinear time-history analyses further demonstrate that pin dowel connections provide better drift control and achieve higher collapse margin ratios than the bolted alternatives, with improved performance in lower-rise configurations. These findings support the use of the developed analytical method as a practical tool to help designers estimate system ductility and compare TMRF alternatives before conducting computationally demanding nonlinear dynamic analyses, while also improving understanding of the overall seismic behaviour of TMRF systems.