## 4 Full-Scale PCS Response Analysis and Optimization Under Traffic Load  
### Structural Response Analysis  
The following three distinct traffic load conditions are considered in this study: (1) external eccentric loading, (2) internal eccentric loading, and (3) full loading. Eccentric loading is considered the most critical stress condition [46; 47; 48; 49]. External eccentric loading applies the load to the outer side of the cantilever, away from the mountain, resulting in outward bending moments. In contrast, internal eccentric loading places the load on the cantilever's inner side, near the mountain, generating inward bending moments. Full loading distributes the load evenly across the entire structure, representing the maximum load the structure experiences during regular operation. Figure 11a illustrates the schematic of load distributions for  
Figure 11: Traffic loading diagrams: (**a**) three loading scenarios; (**b**) lane load diagram; (**c**) vehicle load diagram; (**d**) external eccentric loading diagram; (**e**) internal eccentric loading diagram; and (**f**) full load distribution diagram.  
Figure 12: Stress distribution of the cantilever beam under external eccentric loading.  
Figure 13: Stress distribution of the cantilever beam under internal eccentric loading.  
Figure 13 shows that, compared to external eccentric loading, internal eccentric loading results in higher stress values and a larger stress area in the concrete at the cantilever-column joint, with a maximum principal stress of 2.6 MPa (Figure 13a). The stress in the reinforcement mesh and bolts significantly increases, reaching the maximum principal stresses of 90.5 MPa (Figure 13b) and 77.8 MPa (Figure 13c), respectively. These findings indicate that internal eccentric loading exerts a greater impact on the structure's stability, highlighting its critical role in the overall performance of the cantilever beam. It is noteworthy that under external eccentric loading, the stress in the concrete is lower than that under internal eccentric loading. This is because the internal section of the beam is longer than the external section. Therefore, even though the internal section is adjacent to the mountainside, the longer internal side leads to higher stress in the internal part, whereas the external section experiences comparatively lower stress under external eccentric loading.  
Under full loading, the concrete stress distribution in the cantilever beam is uniform across its middle and upper sections, with the highest principal stress observed at the bottom of the joint, reaching a peak value of 2.9 MPa (Figure 14a). The maximum stress in the reinforcement mesh is similarly concentrated at the bottom of the joint, with a value of 24.4 MPa (Figure 14b). The bolts experience significant stress at their top sections, with the maximum stress reaching 59.2 MPa (Figure 14c).  
The stress analysis across different loading conditions reveals that the beam-column joint experiences the highest stress concentration under internal eccentric loading. In this case, both the reinforcement mesh and bolts exhibit significantly higher stress compared to other scenarios, while the concrete also endures considerable stress. However, given that the reinforcement's yield strength is 345 MPa, the structural reinforcement remains highly reliable. On the other hand, the maximum tensile strength of C50 concrete, at only 4.1 MPa [50; 51; 52], indicates that the safety margin of the concrete is considerably lower than that of the reinforcement. Consequently, to enhance the structure's performance under long-term traffic loads, further optimization efforts are incorporated in this study.