# Effect Mechanism of Connection Joints in Fabricated Station Structures
## 3 Structure Introduction and Ground Motion Input
### The 3D Finite Element Models of Fabricated Station Structures  
The three-dimensional finite element model of the soil-subway station structure system was established in ABAQUS. In order to pay attention to the influence of joint distributions on the fabricated station structure, the finite element model of Changchun Yuanjidian station (defined as the CC model) was first established. Then, the contact surface of prefabricated blocks A and B was simulated with the \"Tie\" feature in Fuchunjiang  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Soil Layer** & **Name** & **Thickness** & **Density** & **Shear Wave** & **Poisson’s** \\
**Number** & & **(m)** & **(kg.m\({}^{-3}\))** & **(m\(\cdot\)s\({}^{-1}\))** & **Ratio** \\ \hline
1 & Miscellaneous fill & 3 & 1900 & 115 & 0.37 \\
2 & Silty clay & 5 & 1950 & 158 & 0.32 \\
3 & Silty clay & 15 & 1980 & 299 & 0.27 \\
4 & Weather & 37 & 1990 & 317 & 0.35 \\  & mudstone & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: The physical and mechanical parameters of the soil.  
Figure 4: The construction process of the fabricated station structure of Changchun Yuanjidian Station, China.  
Figure 3: Fabricated subway station structures with different joint distributions.  
Road Station of Qingdao (defined as the QD model). Finally, the \"Tie\" feature was used to simulate Shenzhen Longxing Station (defined as the SZ model) regarding the contact surface of the prefabricated blocks D and E. The CC model was used as the fundamental model, where its finite element model and prefabricated components are shown in Figure 5. The station's main body is a single-arch and double-layer horseshoe structure, with a total width of 20.5 m and a total height of 17.45 m. The standard ring width of the station structure is 2 m, and the single ring structure is assembled from seven blocks of A, B (left BL, right BR), C (left CL, right CR), D, and E blocks. The connection joints of the prefabricated components mainly include three parts: vault joint (D-E joint), bottom plate joints (A-BR joint, A-BL joint), and sidewall joints (BR-CR joint, BL-CL joint, CR-D joint, CL-E joint).  
The hexahedral C3D8R (three-dimensional eight-node hexahedron reduced integration) element was used in the finite model of structure and soil. The thickness of the fabricated station structure was 2 m, and the damping ratio of the structure was ignored. According to the position and size of the station in the soil, the depth of the intercepted soil model was 60 m, the width of the soil was more than three times that of the station structure, and the width of the intercepted soil model was 150 m. In order to ensure calculation accuracy and efficiency, the mesh size of the soil and structure should meet the requirements:  
\[\Delta X_{\text{max}} =(1/6\,\sim 1/8)c_{\text{min}}/f_{\text{max}} \tag{5}\]  
where \(\Delta X_{\text{max}}\) is the maximum size of the grid, \(c_{\text{min}}\) is the minimum shear wave velocity, and \(f_{\text{max}}\) is the dominant frequency of the input seismic wave.  
According to soil's physical and mechanical parameters, the minimum shear wave velocity was 115 m/s, the maximum dominant frequency of input seismic wave was 3 Hz, and the maximum mesh size should be less than 4.8-6.4 m. According to previous research experience and computer performance, the size of the structure grid was 0.2 m, and the size of the soil grid was 0.5-2 m.