# Experimental Study on Ice Melting of Bridge Tower Crossbeams under Different Conditions
## 3 Results and Discussion
### Crossbeam Ice Melt Test
#### 3.2.2 Effect of Wind Speed on Crossbeam Ice Melt  
The effect of wind speed on the de-icing of the crossbeam is analyzed by comparing the test results of working condition 8, working condition 9, and working condition 10 with those of working condition 5, working condition 6, and working condition 7. Figure 18 shows the variation curves of the average internal temperature of the beam model with time at ambient temperatures of \(-5\)\({}^{\circ}\)C, \(-10\)\({}^{\circ}\)C, and \(-15\)\({}^{\circ}\)C, where the dashed horizontal and vertical coordinates represent the time and temperature corresponding to the start of melting ice on the beam, respectively, where the test conditions were as follows: wind speed of 4.5 m/s, rainfall of 30 mm/h, carbon fiber heating line energized for 1 h, and temperature measurement for 8 h. The temperature rise test results for the average internal temperature of the electrically heated beam model at different ambient temperatures are shown in Table 8. The HD camera video shows that the ice column on the crossbeam started to melt at 22 min, 75 min, and 141 min in the tests for condition 8, condition 9, and condition 10, respectively, and the average critical temperatures at which the crossbeam started to melt were 1.28 \({}^{\circ}\)C, 1.31 \({}^{\circ}\)C, and 1.34 \({}^{\circ}\)C, respectively. The graphs of the changes in the internal temperature field of the beams in test conditions 8, 9, and 10 are shown in Figure 18. It can be seen from the graph that in the three sets of different ambient temperature tests, the temperature rise rate of the internal temperature of the beam was faster in the time range of 0-2 h. In the eighth set of tests in the time range of 2-8 h, the temperature rise rate decreased compared with that occurring at 0-2 h; in the ninth set of tests in the time range of 2-6 h, the temperature rise rate decreased compared with that occurring at 0-2 h; and in the time range of 6-8 h, the temperature rise rate tended to be stable. In the tenth set of tests in the time range of 2-3 h, the temperature rise rate decreased compared with that occurring at 0-2 h, and in the time \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \begin{tabular}{c} **Ambient** \\ **Temperature** \\ **(\({}^{\circ}\)C)** \\ \end{tabular} & \begin{tabular}{c} **Initial** \\ **Temperature** \\ **(\({}^{\circ}\)C)** \\ \end{tabular} & \begin{tabular}{c} **4 h** \\ **Temperature** \\ **(\({}^{\circ}\)C)** \\ \end{tabular} & \begin{tabular}{c} **0–4 h** \\ **Temperature** \\ **(\({}^{\circ}\)C)** \\ \end{tabular} & \
\begin{tabular}{c} **4–6 h** \\ **Temperature** \\ **(\({}^{\circ}\)C)** \\ \end{tabular} &
\begin{tabular}{c} **8 h** \\ **Temperature** \\ **(\({}^{\circ}\)C)** \\ \end{tabular} \\ \hline \(-5\) & \(-3.69\) & \(5.84\) & \(4.77\) & \(9.31\) & \(0.87\) & \(10.38\) \\ \(-10\) & \(-8.68\) & \(3.07\) & \(5.88\) & \(7.31\) & \(1.06\) & \(7.94\) \\ \(-15\) & \(-9.99\) & \(-0.97\) & \(4.51\) & \(1.03\) & \(0.5\) & \(1.3\) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Temperature rise test results for average internal temperature of electrically heated crossbeam specimens at different ambient temperatures. Figure 17: Temperature–time variation curves inside the beam at different ambient temperatures. (**a**) Ambient temperature \(-5\)\({}^{\circ}\)C. (**b**) Ambient temperature \(-10\)\({}^{\circ}\)C. (**c**) Ambient temperature \(-15\)\({}^{\circ}\)C.  
range of 3-8 h, the temperature rise rate tended to be stable. In the tenth group of trials, the rate of temperature rise decreased from that occurring at 0-2 h in the time period at 2-3 h and levelled off at 3-8 h.  
The corresponding mean temperatures at 2 h of heating were 5.84 \({}^{\circ}\)C, 3.07 \({}^{\circ}\)C, and \(-0.97\)\({}^{\circ}\)C, respectively. The ambient temperature of \(-15\)\({}^{\circ}\)C in the test group started to stabilize after 2 h of heating, whereas the other two test groups were still in slow warming at this time.