Cohesive zone model-integrated hybrid numerical simulation strategy for RC/PC beam-column joints under reversed cyclic loadings

Beam-column joints represent one of the most prevalent connection types in modern reinforced concrete structures. Their seismic performance and fracture behavior under strong earthquakes critically govern structural safety, while variations in their detailing configurations lead to significant differences in mechanical response and failure modes. Simultaneously accounting for the hysteretic performance and apparent fracture behavior of precast concrete (PC)/cast-in-situ reinforced concrete (RC) joints in simulation methods has always been challenging. This study proposes an innovative simulation strategy by combines cohesive zone model (CZM) with three-dimensional (3D) model, referred to as the dual-layer model. The 3D model simulates the hysteresis loops, deformation, and energy dissipation of PC/RC joints, while CZM layer captures their fracture behavior at local level. The boundaries are individually tied to achieve time-sequence synchronization deformation. To address the ambiguity in determination the compressive stiffness recovery factor (w_c) in the concrete damaged plasticity (CDP) model, a calculation method for the stiffness recovery path is developed by integrating the CDP model with the focus points model. Furthermore, based on the principle of area equivalence and the concept of multilevel damage zoning, a calibration method is established to determine w_c, and the interval separation point of damage which is related to connection parameters is introduced. Subsequently, verification and comparative analysis are conducted on three PC/RC beam-column joints with varying connection stiffness and configurations. Verification results between simulation and experiment indicate that nearly all backbone points errors below 15 %. Acceptable consistency is demonstrated in stiffness, load-bearing capacity trends, and energy dissipation before and after cracking. The visual similarity of the failure patterns exceeds 60 % across all specimens. The modeling adequacy of the CZM layer and the w_c configuration is confirmed through comparative analysis.