## 3 Numerical Validation and Results
### Prestress Loss
The stress distribution of the superstructure with and without joint damage was also investigated, and the result is presented in Figure 19. Two conclusions can be found: (a) From the perspective of a single segment at the joint damage location in Figure 19a, it can be observed that the stress amplitude on the top plate of the box girder decreased due to adjacent joint damage. This indicates a reduction in load-bearing proportions for the segment, resulting from a loss of connection stiffness. (b) As the load proportion on the mid-span segment decreases, stress will be transferred to its adjacent segments, as illustrated in Figure 19b. Furthermore, joint-degradation-induced stress redistribution had a limited impact on distant segments, at least under current applied vehicle loads. Actually, the impact of joint damage is generally significant for small-span CPCR bridges. The reason for this is that in the case of a small span, the proportion of shear force acting on the beam becomes greater, thereby amplifying the significance of shear stiffness loss caused by joint damage. In this case, the necessary solutions should be implemented when adjacent beam connection failures occur. The failure of concrete joints is typically categorized into three types: longitudinal bridge separation, the vertical displacement of joints and the transverse shifting of joints. To address the issue of longitudinal bridge separation in joints, the most effective approach generally involves applying external prestressed tendons or installing steel plates or CFRP sheets at the joint location. In terms of addressing the vertical displacement and transverse shifting of joints, increasing the friction coefficient between joints can be achieved by incorporating concrete tooth blocks or shear keys at the joint position to prevent any dislocation between them. The previous argument suggests that the impact of horizontal and vertical prestress loss on the overall stiffness of the structure is limited. However, it has a significant effect on the local stress of segments, as demonstrated in Figure 20a. The reduction in transverse  
Figure 20: Performance comparison between prestress loss Case III and no-loss condition. (a) Stress distribution from 3/8 to 5/8 span range. (b) Displacement distribution of mid-span segment. prestress resulted in a significant decrease in residual compressive stress within the box girder, thereby inducing an increase in local deformation, especially in the cantilever position on both sides of the top plate, which can be clearly verified in Figure 20b. The increase in displacement was positively correlated with the loss rate. The loss of longitudinal prestress has a significant impact on both global and local stresses. Figure 21a illustrates the distribution law of principal stress flow in the 270 m main span of the bridge, where the blue arrow indicates the direction of larger compressive stress flow. The results indicate that the proportion of maximum stress at the end decreased significantly with longitudinal prestress loss, while only limited changes in the amplitude and direction of stress flow were witnessed at other positions along the main span. As all longitudinal prestressed steel strands of the top and bottom plates traversed through the mid-span section, the loss in longitudinal prestress had the most pronounced impact on the mid-span local stress distribution. The stress, considering the 29% prestress loss in the mid-span section, is illustrated in Figure 21b, indicating a reduction in stress at both the top and bottom plates compared to the no-loss condition. By comparing the above factors, it can be concluded that the occurrence of bridge defects will have an impact on the local mechanical properties of the box girder in the large-span CPCR bridge, among which the transverse and longitudinal prestress combination loss has the biggest influence, and the change in local stress caused by the time-dependent property of concrete has the least.