A ductile self-centring joint for low-damage design of hybrid timber-concrete bridges

This paper presents an advanced seismic design concept for bridge structures using Ductile Self-Centring Joint (DSJ) that enables highly resilient, low-damage performance under major earthquake events. The DSJ integrates a central rotational bearing with multiple Resilient Slip Friction Joints (RSFJs), arranged to provide controlled rocking, flag-shaped hysteresis, and self-centring capability. This configuration allows the joint to emulate the behaviour of a plastic hinge while avoiding inelastic deformation in concrete members, thereby addressing long-standing challenges associated with damage accumulation, residual drift, and post-earthquake repairability in conventional ductile bridge systems. A comprehensive suite of nonlinear analyses—including nonlinear static pushover, cyclic pushover, and nonlinear time-history simulations—was performed on a three-span timber-concrete hybrid bridge with timber beam composite with concrete deck and integral diaphragms at supports modelled in SAP2000 to evaluate the joint’s global and local seismic performance. The DSJ was modelled using friction–spring link elements to capture RSFJ hysteresis, combined with a rotationally free bearing to accommodate uplift and rocking. Results show that the introduction of DSJs significantly reduces seismic demands: base shear and peak acceleration decreased by up to 65% and 64%, respectively, compared with a conventional elastic low-damage configuration. Equivalent viscous damping ratios of approximately 20% were achieved, and displacement demands were substantially reduced across a broad suite of matched near-fault and far-field ground motions. RSFJ hysteresis loops remained fully elastic throughout all analyses, confirming the self-centring mechanism and absence of structural damage. Overall, these findings demonstrate that the proposed DSJ offers a practical, replaceable, and highly effective solution for next-generation low-damage seismic bridge design.