# Dynamic Load Test and Contact Force Analysis of the AERORail Structure
## 2 AERORail Test Line with Modal Test
### Test Line Structure
#### 2.1.1 Superstructure of the Test Line  
The track adopts a 43 kg/m standard section rail, and its section parameters are shown in Figure 3 and Table 1. The cable components are \(\phi\)15.24 steel strands, with 5 cables on one side and two bundles in total, arranged under the rail. The horizontal spacing of the rails is 1.5 m, and a horizontal tie rod is arranged every 5 m in the longitudinal direction as a horizontal connection. The standard span layout is shown in Figure 4.  
Figure 3: General layout of the AERORail test line.  
A single transverse connecting rod is composed of steel pipes and clamps at both ends. At the position of the pier column, the bowl buckle clamp is used to buckle the top of the pier column; in the position without the pier column, the claw clamp is used to buckle under the rail. Through preliminary tests, it is determined that the vertical spacing of horizontal couplings should not be too large or too small. Too small a spacing will lead to a waste of material, while too large a spacing will make the overall structure and even the track out-of-plane unstable; too large a spacing may also lead to unbalanced load distribution on both sides of the structure. According to the finite element analysis of the upper load, the horizontal arrangement of the free length of the track is approximately 5-8 m. The vertical strut is designed with the support plate and the steel pipe, and its total length is determined according to the shape of the cable and the position of the support.  
In this test line, the pole-support heights used for cables with different spans are shown in Table 1 below:  
At the top of the pier, the cable needs to pass through the reserved channel, and there is a certain angle. When the cable is prestressed and loaded with live load, a certain slip occurs here, which is similar to the slip of the main cable of a suspension bridge when the bridge is completed. This kind of sliding plays a very important role in balancing the force and prestress of the two adjacent spans; the appropriate structural measures should be used to ensure sliding instead of a fixed restraint to reduce the effect of horizontal force on the support column and its instability. In addition, because the edge of the steel member tunnel itself is difficult to ensure smoothness, and its edges and corners form local stress concentration on the cable body, it is very easy to damage the cable body, so structural measures should be taken to solve it. To solve these two problems, this test line uses the construction method of laying tetrafluoroethylene sliding plates in the tunnel to address the tunnel on the top of each pier.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Span** & **1-12** & **13–22** & **23** & **24–25** \\
**Number** & & & & & \\ \hline span(m) & 5 & 10 & 15 & 5 \\ \hline pole position & mid-span & mid-span & mid-span & quarter point & mid-span \\ \hline strut design & & & & & \\ length (mm) & 100 & 200 & 340 & 200 & 100 \\ \hline actual length & & & & & \\ of strut (mm) & 100 & 206–210 & 340–341 & 208–210 & 100 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Summary of the height of each span strut.  
Figure 4: Schematic diagram of the segment of the AERORail test line.