# Research on Optimization Design of Geometric Parameters of a Novel Frame-Embedded Track (NFET)
## 3 Establishment of a Finite Element Model of NFET  
### Track Structure Parameters  
The track slab is made up of two parts: a base body and two prefabricated rail seats. The prefabricated rail seats are connected by three beams to form a prefabricated frame structure. The upper surface of the base body is provided with the first and second grooves, which are perpendicular to each other and, respectively, matched with the rail seats and the cross-beams. The beam divides the base body into different areas, and the drainage wells and cable wells are independently arranged in different areas. A drainage pipe and a cable pipe are, respectively, arranged on the side of the drainage well, and the side wall of the cable well to communicate with the outside of the base body. The beam is also provided  
Figure 3: Schematic diagram of NFET structure.  
with a drainage hole, and the distance between the drainage hole and the bottom of the beam is exactly the depth of the second groove.  
Therefore, according to the structure of NFET, the main geometric parameters for the preliminary design are shown in Table 1.  
The rail seat is prefabricated in the station yard with C50 concrete [19], the track slab is poured on site with C40 concrete, and the steel rail is 60R2 groove steel rail. The detailed calculation parameters are shown in Table 2. Additionally, the model of the NFET was established using a general finite element software called ABAQUS, as shown in Figure 4. The rails are simulated by the beam element, and the filling is simulated by the spring element Cartesian. The standard prefabricated rail seats, cast-in-place concrete, and subgrade are all simulated by solid elements [20; 21; 22]. The rails are simulated by two elastic long beams, which are completely constrained at both ends. The wrapping material is simplified to point-supported linear springs, and each track slab is designed according to 10  sets of fastener nodes. The track slab below the fastener nodes is coupled to one fastener node and connected with the rail node by vertical spring elements. The binding constraint is set between the prefabricated rail seats and the cast-in-place concrete and between cast-in-place concrete and the subgrade. The bottom of the subgrade is completely constrained.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Components** & **Geometric Parameter** & **Value (mm)** \\ \hline Prefabricated frame structure & Length & 5600 \\  & Width & 2026 \\  & Height & 280 \\  & Length & 966 \\ Beam & Width & 185 \\  & Height & 280 \\ Cable pipe & Radius & 80 \\  & Length & 400 \\ Center shaft & Width & 400 \\  & Height & 270 \\ Drainage pipe & Radius & 80 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The main geometric dimensions of NFET.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Track Structure Components** & **Parameter** & **Value** \\ \hline  & Elastic modulus & \(2.1\times 10^{5}\) MPa \\ Rail & Poisson’s ratio & 0.3 \\  & Density & \(7.85\times 10^{-9}\) t/mm\({}^{3}\) \\ Wrapping material & Stiffness & 50 kN/mm \\  & Elastic modulus & \(3.45\times 10^{4}\) MPa \\ Prefabricated rail seat & Poisson’s ratio & 0.167 \\  & Linear expansion coefficient & \(1.0\times 10^{-5}\) \\  & Density & \(2.5\times 10^{-9}\) t/mm \\  & Elastic modulus & \(3.25\times 10^{4}\) MPa \\ Cast-in-place track slab & Poisson’s ratio & 0.167 \\  & Linear expansion coefficient & \(1.0\times 10^{-5}\) \\  & Density & \(2.5\times 10^{-9}\) t/mm\({}^{3}\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Track structure parameters.