## 3 Calculation Results and Analysis
### Analysis of Calculation Results in Case 2  
The horizontal and vertical displacement maps of the model as a whole when the settlement of the hanging wall is 10 cm, 20 cm, 30 cm, 40 cm, and 50 cm in the middle span of the overpass span riding ground fissure condition are shown in Figure 6.  
The horizontal displacement at the top and bottom of the pier is determined, as shown in Table 5. The slope of each pier at different settlement amounts is shown in Figure 7. When the settlement amount is 50 cm, the slope of the No. 1 bridge pier at the footwall of the ground fissure is the largest in the settlement process, with a slope of 0.64%. Pier No. 2 of the footwall of the ground fissure takes second place, with a dip of 0.54%. Pier No. 4 at the hanging wall inclines by 0.50%. Additionally, the tilt of 0.12% of Pier No. 3 located on the hanging plate is the smallest. It is observed that when the vertical settlement of ground fissures exceeds 10 cm, the slope of the bridge pier may exceed the specification requirements.  
The vertical displacement of the nodes at the left and right ends of each span of the box girder is shown in Table 6, and the inclination of each box girder under different settlement amounts is shown in Figure 8. When the settlement is 50 cm, the mid-span box girder across the ground fissure has the largest inclination, which is 0.96%, followed by the left side of the footwall of the ground fissure, with a slope of 0.44%. The right side of the upper wall of the floor fissure has the smallest inclination, which is 0.32%. When the vertical settlement of the ground fissure exceeds 10 cm, the mid-span inclination across the ground fissure exceeds the standard limit.  
During the settlement of the hanging wall of the ground fissure, a large longitudinal stress is generated in the box girder. The stress map for when the settlement is 10 cm is shown in Figure 9.  
Figure 5: Longitudinal stress of box girder under 10 cm settlement.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Vertical** \\ **Settlement** \\ **fem** \\ \end{tabular} } & \multicolumn{2}{c}{\begin{tabular}{c} **Bridge Pier 1** \\ **Top** \\ **Displacement** \\ **/mm** \\ \end{tabular} } & \multicolumn{2}{c}{\begin{tabular}{c} **Bridge Pier 2** \\ **Bottom** \\ **Displacement** \\ **/mm** \\ \end{tabular} } & \multicolumn{2}{c}{\
\begin{tabular}{c} **Bridge Pier 3** \\ **Bottom** \\ **Displacement** \\ **/mm** \\ \end{tabular} } & \multicolumn{2}{c}{
\begin{tabular}{c} **Bridge Pier 4** \\ **Bottom** \\ **Displacement** \\ **/mm** \\ \end{tabular} } \\ \hline
10 & 2.266 & 1.058 & 2.099 & 1.411 & 2.143 & 1.678 & 2.340 & 1.159 \\
20 & 4.543 & 2.075 & 4.208 & 2.656 & 4.323 & 3.580 & 4.713 & 2.456 \\
30 & 6.554 & 2.895 & 6.000 & 3.404 & 6.195 & 5.321 & 6.816 & 3.710 \\
40 & 8.388 & 3.620 & 7.582 & 3.881 & 7.857 & 6.880 & 8.732 & 4.911 \\
50 & 10.110 & 4.307 & 9.038 & 4.215 & 9.388 & 8.297 & 10.531 & 6.061 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Horizontal displacement of bridge pier.  
It is observed that the maximum tensile stress in the box girder is 12.5 MPa, while the ultimate tensile stress of C50 concrete is 5 MPa, which means that tensile damage to the box girder concrete occurs when the settlement of the ground fissure joint activity is greater than 10 cm.  
Figure 6: Overall displacement map under different settlements of the hanging wall of the ground fissure: (**a**) S = 10 cm; (**b**) S = 20 cm; (**c**) S = 30 cm; (**d**) S = 40 cm; (**e**) S = 50 cm.