## 4 The Dynamic Behavior of the Cable under the Action of the Train  
To simplify the analysis and save computing resources, the moving loads method [30] that simplifies the train to several concentration forces applied on the bridge was adopted to simulate the train driving through the bridge. The train prototype was the CRH3 electric multiple unit (EMU), consisting of eight carriages [31]. An empty EMU weighs 380 tons, and an EMU has a seating capacity of 601 people. Assuming that the average weight per person is 80 kg (People's Republic of China Ministry of Railways 2001), each carriage's weight is G = 53,510 kg. Because one carriage is supported by eight wheels, the load model of the carriage is divided into eight point loads, so the vertical excitation force generated by a wheel is F = G/8 \(\times\) 9.8 N/kg = 65,549.75 N [32]. The moving loads of two EMUs with 16 carriages are grouped as 16 \(\times\) 8 \(\times\) F. The train load is shown in Figure 7.  
The bridge was equipped with a structural health monitoring (SHM) system, which was detailed in reference [28], and the data recorded by the displacement sensors and acceleration sensors installed at the midspan of the main span near the downstream side could be used to verify the accuracy of the FEM. The comparison of the deflection and acceleration temporal curves between the monitoring data and simulated data is shown in Figure 8 and Table 3. It could be found that the deflection data from the FEM simulation was coincident with that from the SHM system, and neither of them showed obvious vibration characteristics. For the acceleration result, the simulated data were much smaller than the monitoring data at the beginning and end stages, but there was little difference after the train drove to the main span. This may have been caused by ignoring the wind influence during the simulation. The analysis above indicates that the FEM is accurate enough to simulate the real bridge, and the moving loads method is meaningful in this research. Figure 7: The moving load applied on the bridge: (**a**) the train model; (**b**) the local moving load diagram; and (**c**) the whole moving load diagram. Considering the symmetry of the bridge, only the load case where the train drives from the west side to the east side on the downstream tracks was analyzed. The spatial distribution of the extreme value of the displacements and accelerations at the connection of the beam and cables for each of the 38 cables on the upstream and downstream sides near the west side is given in Figure 9. The amplitude of the displacements under the moving loads was taken as the difference between the initial deflection and the minimum value of the deflection temporal curves. It could be found that the deflection and acceleration amplitudes near the train driving side were larger than those away from it, but the trends of both curves were similar. The maximum value of displacement amplitude occurred at the longest cable near the middle of the main span (No. 38). The cable at the side span of the bridge was relatively less affected by the train load, mainly because the side span was shorter than the main span. Thus, the bridge deflection was smaller under the train load, and this phenomenon could also be verified by the data from the bridge's SHM system, which were analyzed by [PERSON] et al. [28]. The acceleration amplitude from the bridge bank to the middle of the side span showed a trend of gradual increase. In contrast, the change from the middle of the side span to the middle of the main span was not significant, mainly because the train had not yet wholly entered the bridge at the beginning; the amplitude of the vibration generated by the train gradually increased along with the train entering the bridge and tended to be stable after the train had fully entered the bridge. The amplitude of displacement and acceleration was higher at the connection between the cable and the main girder near the side where the train load was located.