Time-Dependent Seismic Performance Evaluation of Precast Concrete Frame Joints Affected by Chloride Ion Corrosion in Coastal Atmospheric Environments

Precast concrete frame joints in coastal atmospheric environments are susceptible to mechanical performance degradation caused by chloride-induced corrosion, yet joint-scale numerical studies incorporating multi-indicator time-dependent mechanical responses remain limited. This paper presents a coupled framework that integrates chloride diffusion, corrosion, and finite-element analysis for a typical precast beam–column joint to evaluate the relative changes in seismic performance indicators across service ages of 0, 15, 30, 40, and 50 years. The numerical model was baseline-validated against uncorroded and corroded test specimens under cyclic loading. Time-dependent models accounting for chloride diffusion, rebar corrosion, and material strength degradation were implemented. The elastic modulus reduction was restricted to the damaged covering concrete rather than the intact internal concrete. The simulation results show that mechanical degradation is limited in the early service stage, whereas hysteretic pinching and deformation-related deterioration become more pronounced with increasing service age. By 50 a, the peak load-bearing capacity has decreased by 13.68%, whereas the ultimate displacement and ductility coefficients have declined by 15.10% and 37.40%, respectively. These results should be interpreted as case-specific predictions under the adopted cover thickness, chloride exposure condition, and material parameters rather than as universal deterioration thresholds. The findings indicate that service-life evaluations of precast joints in coastal atmospheric environments should not rely solely on strength indicators but should also incorporate stiffness, ductility, and energy dissipation capacity.