## 4 Results
### Dynamic Response
#### 4.3.3 Running Posture  
Furthermore, the DC and WLRR and based on the coordinate system given in Figure 4, the train-bridge coupled dynamic system provides the posture with respect to changes in the train passing through the crosswind area under different wind barrier conditions and at different speeds. As in Sections 4.3.1 and 4.3.2, the changes and acceleration of the head car in five degrees of freedom (lateral and vertical displacement and rotation in three directions) were compared and analyzed. Figure 15 shows the changes of different degrees of freedom indexes when the train passed the bridge under the protection of different heights of the windshield. In the figure, Dy, Dz, Rx, Ry, Rz are the lateral and vertical displacements (unit: m) of the head car and the rotation of the x, y, and z axes (unit: rad). Figure 16 shows their acceleration, where Ay,  
Figure 14: Time-varying WLRR values of the first wheelset of the head car with various running speeds: (**a**) 200 km/h; (**b**) 250 km/h; (**c**) 300 km/h; (**d**) 350 km/h. Figure 13: Time-varying WLRR values of the first wheelset of the head car with various wind-protection conditions: (**a**) H = 0 m; (**b**) H = 2 m; (**c**) H = 4 m; (**d**) H = 6 m.  
Az, A\({}_{\rm Rx}\), A\({}_{\rm Ry}\), A\({}_{\rm Rz}\) are the accelerations of Dy, Dz, Rx, Ry, Rz, respectively. The diagram of the running posture of the train is also given in each figure, where the transparent one means the original position, and another is the posture caused by the crosswind. As shown in Figure 15a, when the train entered the crosswind region, a displacement corresponding to the crosswind was applied to the train, among them, the 0 m and 2 m height barriers could not effectively reduce this displacement, while the 4 m height barrier always kept the head car move laterally with 0.01 m, which was regarded as the best wind-protection effect. However, a displacement opposite to the crosswind direction was found at the train under a 6 m height wind barrier due to the over-protection. The crosswind raised the height position of the head car while the barriers weakened this effect, where the 4 m height and 6 m height gave a similar response, as shown in Figure 15b. The crosswind tended to provide a negative Rx value to make the train overturn, where the 2 m height wind barrier seemed not to bring any protection. Same as the performance of the Dy, the 4 m height barrier effectively decreased the Rx while the higher one gave an over-protection. Many fluctuations were found in the change in Ry; the presence of the wind barriers always provided a good reduction in the Ry value to ease the pitching moment of the head car. As shown in Figure 15d, the varying yawing moment showed a sensitive change to the height of the wind barrier. As shown in Figure 16, the difference among the accelerations along five degrees of freedom of the head car was not as evident as the displacements and rotations. Although the wind barrier can effectively maintain the running posture of the train in the crosswind region, its existence will bring greater fluctuations when the train enters or leaves the barrier region. Figure 16: Time-varying values of the accelerations along five degrees of freedom of the head car with various wind barriers: (a) Ay; (b) Az; (c) A\({}_{\rm Rx}\); (d) A\({}_{\rm Ry}\); (e) A\({}_{\rm Rz}\). Figure 15: Time-varying values of the indicators along five degrees of freedom of the head car with various wind barriers: (a) Dy; (b) Dz; (c) Rx; (d) Ry; (e) Rz. Similarly, Figure 17 shows the changes of different degrees of freedom indexes when the train passed the bridge at different speeds, and Figure 18 gives their accelerations. In addition to the time difference brought about by different speeds, the sensitivity of Dy and Rx to the running speed of the train was slight, as shown in Figure 17a,c. A higher running speed resulted in smaller Dz and greater Ry and Rz. The acceleration also exhibited complex changes over time, but the peak value of acceleration always increased with increasing speed.