Traditional cast-in-place beam–column joints have the defects of high complexity and high construction difficulty, which seriously affect the efficiency and safety of the building construction line, and precast beam–column joints (PBCJs) can greatly improve the construction efficiency and quality. At present, the investigations on the seismic behavior of precast reinforced concrete structures are still mainly focused on experiments, while the numerical simulations for their own characteristics are still relatively lacking. In the present study, the seismic behavior of novel precast beam–column joints with mechanical connections (PBCJs-MCs) is investigated numerically. Based on the available experimental data, fiber models for four PBCJs-MCs are developed. Then, the simulated and experimental seismic behaviors of the prefabricated BCJs are compared and discussed. Finally, the factors influencing the seismic behavior of the PBCJs-MCs are further investigated numerically. The numerical results indicate that the fiber models can consider the effect of the bond–slip relationship of concrete and reinforcement under reciprocating loads. The relative errors of the simulated seismic behavior indexes are about 15%. The bearing capacity and displacement ductility coefficients of the PBCJs-MCs decrease rapidly as the shear-to-span ratio (λ) increases. It is recommended that the optimum λ for PBCJs-MCs is 2.0–2.5. The effect of the axial load ratio on the seismic behavior of PBCJs-MCs can be negligible in the case of the PBCJs-MCs with a moderate value of λ.

Non-steam-curing ultra-high-performance concrete (UHPC) is a promising material for in situ bridge deck rehabilitation; however, its strength development under variable curing temperatures remains insufficiently understood. This study investigated the coupled effects of curing temperature and constituent dosage on the mechanical performance of non-steam-curing UHPC. Compressive and flexural strength tests were conducted on mixtures incorporating different dosages of silica fume, microspheres, and steel fibers. Based on the experimental results, two predictive models were developed to describe the time-dependent strength evolution of UHPC at the optimal mixture proportion and the later-age strength as a function of curing temperature and constituent dosage. The results showed that silica fume had a significant influence on early-age strength, but its effect was strongly dependent on curing temperature and age. At low curing temperatures, silica fume initially reduced early-age strength, whereas its contribution became positive with prolonged curing. When the microsphere dosage exceeded 55 kg/m³, early-age strength decreased with increasing microsphere content; however, this adverse effect gradually weakened and eventually became beneficial as curing temperature and curing age increased. Increasing the steel fiber dosage from 40 to 160 kg/m³ consistently improved both compressive and flexural strengths, whereas further increases produced only marginal additional enhancement. The proposed models captured the temperature-dependent strength development of non-steam-curing UHPC and provide a quantitative basis for mixture optimization and construction-stage strength prediction in bridge rehabilitation applications.