Study on the plastic hinge relocation mechanism in a novel precast post‐tensioned beam‐to‐column joint

Previous cyclic loading tests on a novel precast prestressed concrete beam‐to‐column joint showed that different design configurations resulted in substantially different seismic responses, depending on whether plastic hinge relocation was successfully achieved. These differences were mainly reflected in the failure mode and energy‐dissipation capacity. To further investigate the underlying mechanism, a refined finite element model was developed using ABAQUS and validated against the experimental hysteresis curves, skeleton curves, cumulative dissipated energy, and failure modes. A parametric study was subsequently conducted to examine the effects of seven design parameters on the proportion of the total rotation occurring at the slotted section, cumulative dissipated energy, skeleton response, and hysteretic behavior. The area of the energy‐dissipating (ED) rebars, the area of the post‐tensioning (PT) strands, the haunch height and length, and the slot depth significantly affect plastic hinge relocation, resulting in corresponding variations in cumulative dissipated energy and peak load. The effective prestress in the PT strands has only a minor influence on plastic hinge relocation and peak load but increases the small‐drift secant stiffness and cumulative dissipated energy. Increasing the concrete strength improves plastic hinge relocation, load‐carrying capacity, and energy dissipation, although the improvement becomes limited beyond a moderate strength level. Comparisons between the finite element results and theoretical moment capacities demonstrate that the ratio of the linear‐limit moment to the required beam‐end moment is an effective indicator of plastic hinge relocation and energy‐dissipation performance, and a conservative ratio of at least 1.0 is recommended for joint design. Finally, a suitable strut‐and‐tie model was developed based on the finite element results to investigate the force transfer mechanism in the precast beams. The predictions of this model are in good agreement with experimental observations, demonstrating its applicability to the design and analysis of the novel joint.