## 5 Temperature Field Analysis of Concrete Bridge Tower
### Temperature Field Analysis  
#### 5.2.1 Surface Temperature Difference Analysis  
Figure 19 shows the shaded state of the bridge tower surface at 10:00 a.m. and the temperature field cloud map at this time. It can be seen from the diagram that the shadow occlusion has a significant effect on the sunshine temperature field of the structure, and the temperature difference between the sunlight area and the shadow area is large. Figure 20 shows the surface temperature changes with the height of the four wall surfaces of the bridge tower (the external surface of the east tower wall, the south tower wall, the west tower wall, and the north tower wall) at 10 a.m. It can be seen from the figure that the shadow has a significant impact on the temperature change of the tower wall surface. The temperatures of the external surfaces of the east tower wall and the south tower wall irradiated by the sunlight are higher than those of the external surfaces of the west tower wall and the north tower wall, which are always in shadow. Because the incidence angle of the sunlight on the external surface of the east tower wall is smaller than that on the external surface of the south tower wall, the external surface of the east tower receives more solar radiation, and its temperature is higher than that on the external surface of the south tower wall. On the external surface of the east tower wall, the surface temperature of the lower tower column is significantly lower than that of the upper tower column and the middle tower column because the lower tower column is in shadow. It can be seen from the above that the influence of shadow shading must be considered when analyzing the three-dimensional sunshine temperature field of the bridge tower. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Date**} & \multirow{2}{*}{**Weather Conditions**} & \multicolumn{2}{c}{**Maximum Temperature/\({}^{\circ}\)C**} & \multicolumn{1}{c}{**Minimum Temperature/\({}^{\circ}\)C**} \\  & & **Temperature/\({}^{\circ}\)C** & **Temperature/\({}^{\circ}\)C** \\ \hline
16 August 2022 & Fine & 34 & 27 \\
17 August 2022 & Fine & 36 & 28 \\
18 August 2022 & Fine & 37 & 27 \\
19 August 2022 & Fine & 37 & 28 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Atmospheric temperature data. Figure 19: Shadow occlusion state and temperature field cloud of the bridge tower at 10:00 a.m. (**a**) The shaded state of the bridge tower surface; (**b**) the temperature field cloud map. Figure 21 shows the change curve of the external surface temperature (\(T\)) of the tower wall at the 125 m height of the bridge tower and the change curve of the temperature difference (\(\Delta T\)) between the opposite sides of the tower columns (the east wall, the south wall, the west wall, the north wall, the inner east side, and the inner west side refer to the wall surface of the measuring points \(T_{1}\), \(T_{2}\), \(T_{3}\), \(T_{4}\), \(T_{5}\), and \(T_{6}\) in the figure, respectively). It can be seen from the figure that in a day, the surface temperature changes are the same; from night to early morning, the surface temperature of each surface was in a state of continuous decline, but the trend of temperature reduction gradually slowed down, reaching the lowest value at about 6 a.m. In the daytime, due to the influence of solar radiation and ambient temperature changes, the temperature of each wall surface showed a trend of rising first and then falling. The temperature of the eastern wall surface, which was first irradiated by the sun, rose faster than that of other surfaces, reaching its maximum at about 10 a.m., followed by the south wall surface irradiated by the sun. However, due to the large incident angle of the sun on the south wall surface, the amount of solar radiation received by the wall surface was small, so the temperature rose slowly. Finally, the west wall surface was irradiated by the sun.