## 4 Full-Scale PCS Response Analysis and Optimization Under Traffic Load
### Structural Optimization Based on the Numerical Design  
The analysis reveals that the concrete in the cantilever beam experiences relatively high stress, with significant stress concentration and limited safety margins. To improve these safety margins, it is essential to reduce stress in the concrete. One effective solution is the addition of prestressed rebars, which help improve stress distribution and mitigate stress concentration. Prestressing not only counteracts tensile stress in the concrete but also significantly enhances the structure's crack resistance and overall stiffness [53; 54; 55]. Based on the findings from Section 3.1, where concrete stress is mainly concentrated at the bottom of the inner end of the beam, three configurations for prestressed rebar placement are proposed, which are illustrated in Figure 15, as follows: Case 1, where prestressed rebars are placed at the upper inner side of the cantilever beam; Case 2, where prestressed  
Figure 14: Stress distribution of the cantilever beam under full loading. rebars are positioned on both the upper inner and outer sides of the cantilever beam; and Case 3, which builds on Case 2 with additional prestressed rebars at the bottom of the inner beam. Each configuration includes six rebars with a 28 mm diameter, spaced 100 mm apart (D28@100), and prestressed to 300 MPa. The main reason for adopting a very low prestress level (300 MPa) in prestressed elements is to prevent the occurrence of unacceptable cracks due to excessive stresses on the components during transportation [22; 56]. A lower prestress level reduces the risk of damage during transportation, especially when the components are subjected to transportation vibrations or other external loads. The reduced stress helps effectively decrease stress concentration in the material, thus preventing cracks from forming. Figures 16-18 display the stress distribution of both the original and optimized cantilever beams with prestressed rebars under the following three loading conditions: external eccentric load, internal eccentric load, and full load. Figure 16 illustrates the impact of prestressed rebars on the stress distribution under external eccentric loading. The addition of prestressed rebars significantly reduces the tensile stress at the top of the inner side of the beam and the beam-column joint. In Case 1, where prestressed rebars are placed only on the inner side of the beam, the maximum stress is reduced to 1.5 MPa (Figure 16b), although stress concentration remains, particularly at the top of the beam-column joint. In Cases 2 and 3, where rebars are added to both the inner and outer top surfaces, the stress concentration is notably decreased, with the maximum stress values dropping to 1.4 MPa (Figure 16c) and 1.3 MPa (Figure 16d), respectively. This demonstrates that positioning prestressed rebars on both the inner and outer top surfaces significantly reduces stress concentration, thereby improving the bending and shear resistance of the cantilever beam under external eccentric loading. Figure 15: Prestressed rebar arrangement in cantilever beam. Figure 17 demonstrates that the addition of prestressed rebars greatly reduces stress levels in the cantilever beam, particularly at the midsection and the bottom of the beam-column joint, under internal eccentric loading. In Case 1, where prestressed rebars are positioned only on the inner side, the high-stress area at the beam-column joint is reduced, but a concentrated stress zone still exists (Figure 17b). In contrast, Cases 2 and 3, where additional prestressed rebars are placed on the outer beam, further decrease the high-stress area, improving the overall uniformity of stress distribution and reducing the maximum stress. These cases show only a small high-stress region at the bottom of the inner beam-column joint (Figure 17c,d). This suggests that positioning prestressed rebars on both the inner side and the outer beam-column joint is reduced, but a concentrated stress zone still exists (Figure 17c).