# Current Practices of Railway Ballastless Track Design Methods in China
## 3 Case and Calculation Model
### Working Conditions  
When the prefabricated track slab is a unit structure and the foundation is a bridge, the calculating loads mainly include the train load, temperature gradient and bridge deflection. For the LSM, the fundamental combination and coincidence combination are used to check the normal stress of the section, and the standard combination is used to check the crack. As for the ASM, only the main forces are considered in the load combination. To explore the influence of different load parameters on the reinforcement results, it is necessary to set a series of working conditions when determining the load values.  
1. Train load According to the requirements of the Code for the Design of Intercity Railways (TB10623-2014) [36], different train axle loads and speeds will affect the values of the train load, which will also affect the reinforcement results. Therefore, three working conditions are adopted, including a passenger and freight railway with a design speed of 200 km/h (D1), an intercity railway with a design speed of 160 km/h (D2) and an intercity railway with a design speed of 200 km/h (D3). Under different working conditions, the train loads of the LSM and the ASM are shown in Table 2.  
In simulation analysis, the vertical train load is loaded on the center of N5520 track slab in the middle of the bridge, which is the most unfavorable position.  
2. Temperature gradient load The track slab is affected by continuous solar radiation, so it is necessary to consider the temperature load. Because the new prefabricated track slab is a unit structure, only the temperature gradient is considered. In consideration of extreme heat conditions, the vertical positive temperature gradient of the track slab is set from 65 \({}^{\circ}\)C/m to 105 \({}^{\circ}\)C/m; the negative temperature gradient is set from 30 \({}^{\circ}\)C/m to 50 \({}^{\circ}\)C/m, shown in Table 3.  
3. Bridge deflection load It is also necessary to consider the influence of bridge deflection on the track structure. The foundation is a 32 m double-line simply supported box-g  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{3}{*}{\
\begin{tabular}{c} **Working** \\ **Conditions** \\ \end{tabular} } & \multirow{3}{*}{
\begin{tabular}{c} **Static Wheel** \\ **Weight** \\ \end{tabular} } & \multicolumn{3}{c}{**The ASM**} & \multicolumn{3}{c}{**The LSM**} \\ \cline{3-7}  & & **Vertical Load** & **Lateral Load** & **Vertical Load** & **Lateral Load** \\ \cline{2-7}  & \(P_{j}\) & \(\mathbf{\alpha}\) & \(P_{\mathbf{d}}\) & \(\mathbf{Q}\) & \(P_{\mathbf{k}}\) & \(\mathbf{Q}_{\mathbf{k}}\) \\ \hline D1 & 11.5 & 2.5 & 28.75 & 9.2 & 23 & 9.2 \\ D2 & 2 & 17 & & & & \\ D3 & 8.5 & 2.5 & 21.25 & 6.8 & 17 & 6.8 \\ \hline \end{tabular}
\end{table}
Table 2: Train load values.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Working Condition** & **TD1** & **TD2** & **TD3** & **TD4** & **TD5** \\ \hline Positive temperature gradient & 65 & 75 & 85 & 95 & 105 \\ Negative temperature gradient & 30 & 35 & 40 & 45 & 50 \\ \hline \end{tabular}
\end{table}
Table 3: Working conditions of temperature gradient.