To clarify the strengthening mechanism of corrugated plates on the mechanical behavior of longitudinal segmental joints in shield tunnels, a refined three-dimensional finite element model incorporating corrugated plate joints was established. The numerical model was validated using full-scale test results. The enhancement effects of corrugated plate reinforcement on the bending stiffness and ultimate bearing capacity of segmental joints were investigated. Moreover, the influence of axial force, reinforcement timing, and corrugated plate joint configuration on the mechanical performance of reinforced joints was examined. The results indicate that the proposed numerical model can accurately simulate the nonlinear mechanical behavior of corrugated-plate-reinforced longitudinal joints subjected to combined compression and bending, demonstrating good agreement with experimental observations. Under negative bending moments, corrugated plate reinforcement increases the ultimate bending capacity by 29.4%, while the bending stiffness in the elastic-plastic stage and at ultimate failure is enhanced by 101.8% and 40.5%, respectively. When a double-row bolt connection is adopted, the ultimate bending capacity is only 2.6% lower than that of fully welded corrugated plates, and is 31.1% higher than that of a single-row bolt connection. It is therefore recommended to prioritize the double-row bolt configuration to prevent failure at the corrugated plate-segment interface.