## 3 Global Performance of SFTs with Suspension Cables  
In this section, a new concept of suspended SFT models, with two solutions, is suggested, as shown in Figures 5 and 6. Figures 5a and 6b display Type 1, which has towers on both ends and main cables connected to the towers. On the contrary, Type 2, shown in Figure 5b, has an additional anchorage in the middle of both towers. Figure 5b shows the dimensions of Type 1, which are based on anchorages at both towers, and a main cable that connects them and is supported by hangers between the main cable and the tube. In contrast, Figure 6c represents the dimensions of Type 2, in which a form of anchorage is installed at the required position, and the main cable is arranged so that it can control the displacement of the center between the towers effectively. To investigate the global performance of the SFT, the commercial finite element program, ABAQUS AQUA (SIMULIA, IA, USA), was used [14]. This program can consider various ocean environmental conditions, such as irregular waves, currents, etc. Figure 5: Components of the submerged floating tunnel with suspension cables. Finite element model by ABAQUS [14]: (**a**) Type 1; (**b**) Type 2. Furthermore, Figure 6a exhibits the variables of the analysis of the section view of the suspended SFT. It was assumed that both ends are fixed boundary conditions on land. The main span of Type 1 was 1000 m in length, and in Type 2, two arched main cables were installed at the middle anchorage. The towers and main cables were fixed at the anchorages. Moreover, hangers and tethers on the side of the main cables were hinged to the foundation. The environmental conditions and specifications for the SFT model are shown in Table 1. To begin with, the conditions of the model were set as follows: A water depth of 280 m and significant wave heights (periods) of 3.5 m (5 s), 6.0 m (8 s), and 8.0 m (10 s). Moreover, the irregular waves in a time  
Figure 6: Considered suspension SFT: (**a**) section view; (**b**) dimensions of Type 1; (**c**) dimensions of Type 2.  
series, as shown in Figure 7, were applied using the JONSWAP spectrum. [15] The suspended SFT consists of a tube, main cables, hangers, towers and side tethers, as shown in Figures 5 and 6. \begin{table}
\begin{tabular}{l l} \hline \hline
**Parameters** & **Values** \\ \hline
**Environmental condition** & \\ Water depth (m) & 280 \\ Peak wave period (Tp, s) & 5, 8, 10 \\ Significant wave height (Hs, m) & 3.5, 6.0, 8.0 \\
**Tube** & \\ Outer diameter (m) & 17, 20, 23 \\ Thickness of SFT (m) & 1 \\ Span length (m) & 1000 \\ Drag/added mass coefficient & 1.2/1.0 \\ Installation depth (m) & 40, 70, 100 \\
**Main cable (wire, spiral with sheathing)** & \\ Outer diameter (m) & 0.4 \\ Cross sectional area (m\({}^{2}\)) & 0.125 \\ Elastic modulus (GPa) & 205 \\ Minimum yield stress (MPa) & 1180 \\ Maximum yield stress (MPa) & 1570 \\ Drag/added mass coefficient & 1.2/1.0 \\ Inclination angle & 12, 25, 35 \\
**Hanger (wire, spiral with sheathing)** & \\ Outer diameter (m) & 0.32 \\ Cross sectional area (m\({}^{2}\)) & 0.08 \\ Elastic modulus (GPa) & 205 \\ Minimum yield stress (MPa) & 1180 \\ Maximum yield stress (MPa) & 1570 \\ Drag/added mass coefficient & 1.2/1.0 \\
**Side tether** & \\ Outer diameter (m) & 0.379 \\ Cross sectional area (m\({}^{2}\)) & 0.113 \\ Elastic modulus (GPa) & 210 \\ Minimum yield stress (MPa) & 482.6 (API X70) \\ Maximum yield stress (MPa) & 565.4 (API X70) \\ Drag/added mass coefficient & 1.2/1.0 \\
**Tower** & \\ Width \(\times\) Height \(\times\) Thickness (m) & \(10\times 5\times 1\) \\ Compressive strength (MPa) & 35 \\ Elastic Modulus (GPa) & 28.066 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Geometric and environmental conditions for the case study. Figure 7: Wave elevation for the analysis model. Next, the tube of the main body, which is made of reinforced concrete, with a thickness of 1 m, was set to have an outer diameter of 17 m, 20 m, and 23 m. The total length was 1200 m, and the span between towers was 1000 m in length.