## 4 Parametric Study  
### Wave Height  
As previously mentioned in Table 1, the wave condition was selected, with three variables, according to significant wave heights and periods of 3.5 m (5 s), 6.0 m (8 s) and 8.0 m (10 s). These conditions represented the time series, shown in Figure 7, applying the JONSWAP spectrum. The common variables of the analytical model include a BWR of 1.2, a main cable angle of 12 degrees, a tube external diameter of 23 m, and an installation depth of 70 m.  
Figure 12 shows the motion, acceleration, reaction force, section force, and section moment in the SFT, according to wave heights. Figure 12 displays the motion of the suspended SFT, according to the wave height. As the wave height increased, the overall motion tended to grow. Moreover, it can be found that the motion in Type 2 was smaller than that in Type 1. In absolute terms, the heave motion was the largest due to the influence of the BWR, followed by the sway, which was deformation in the wave acting direction.  
Figure 11: Section moment at each point of the SFT: (**a**) section moment at each point of Type 1; (**b**) section moment at each point of Type 2.  
Figure 12: Cont.  
Figure 12b exhibits the maximum acceleration in the SFT, according to the wave height, without considering the position. It can be seen that the absolute maximum value tended in the upward direction as the wave height increased, but in the case of Type 2, the acceleration value significantly rose under the 6 m wave height condition. It can be judged that the acceleration was generated largely by the impact load of irregular waves, as shown in Figure 12a. It can be determined that the acceleration in Type 2 under the 8 m wave height condition was smaller than that under the 6 m condition, because in the case of the 6 m wave height, there was a smaller heave motion than in the case of the 8 m condition.  
Figure 12c plots the maximum reaction force on the foundation of the SFT model, according to wave height, without considering the position. There was less reaction force on Type 2 than on Type 1, because it had one more anchorage to support. In terms of tendency, Type 1 was increased linearly, but in the case of Type 2, the slope was increased at the wave height of 6 m due to the influence of the heave.  
When the wave force acted, cross-section forces, such as the shear force and the moment were generated in the SFT. As mentioned above, an axial force, SFx, was generated in the x-axis in the SFT,  
Figure 12: Behavior of the SFT, according to the wave height: (**a**) motion of the SFT; (**b**) maximum acceleration on the SFT; (**c**) maximum reaction force on the foundation of the SFT; (**d**) maximum section force on the SFT; (**e**) maximum section moment in the SFT.  
and a shear force, SFy and SFz, occurred in the wave load acting direction (y-axis) and the buoyancy direction (z-axis), respectively. These section forces at each point were plotted in Figures 10 and 12d, representing the maximum section force on the foundation of the SFT, according to the wave height. Both Type 1 and Type 2 had the largest shear force, SFy, in the wave acting direction. In the case of Type 1, the section force on the SFT was decreased in the order of SFy, SFx and SFz. On the contrary, since Type 2 was supported by a middle anchorage, there was a lot of shear force, SFy, and not a lot of SFx and SFz.  
Figure 12e plots the absolute maximum section moment at the foundation of the SFT, according to the wave height. It can be seen that the torsional moment (SFx) dominated in both Type 1 and Type 2. It can be considered that the torsion occurred in the arch shaped SFT model, because the wave acted in the y-axis, while heave motion was generated, as shown in Figure 8. For this reason, the torsional moment of Type 1, with the largest heave motion, was greater than that of Type 2.