## 3 Test Results
### Wave Forces According to Wave Periods of Regular Waves  
Table 3 summarizes the maximum amplitudes of the wave forces to wave periods for the real-scale models and Figure 10 plots the maximum amplitude of wave forces obtained under regular waves for the real-scale models of the three types of support structure. The measured wave forces exhibit a similar tendency according to the wave periods regardless of the sea level. According to the change of the wave period, the wave forces decrease gradually with longer wave periods from wave R-#1 (7.5 s) to wave R-#3 (15.5 s) in most of the support structures at the three sea levels [16; 23; 24]. The wave forces show a smaller decrease ratio according to the wave period at HSLW than at MSL and LSWL, with ranges of 0.80-0.97 at HSWL, 0.57-0.70 at MSL, and 0.69-0.78 at the LSWL.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Sea Levels**} & \multirow{2}{*}{**Wave**} & \multicolumn{2}{c}{\(\mathbf{P_{w}}\)} & \multicolumn{1}{c}{**Monopile**} & \multicolumn{1}{c}{**GBS**} & \multicolumn{1}{c}{**Hybrid 0\({}^{\circ}\)**} & \multicolumn{1}{c}{**Hybrid 45\({}^{\circ}\)**} \\ \cline{3-7}  & & **sec** & **kN (Ratio)** & **kN (Ratio)** & **kN (Ratio)** & **kN (Ratio)** \\ \hline \multirow{3}{*}{HSWL} & R-\#1 & 7.5 & 973 (1.00) & 2608 (1.00) & 1140 (1.00) & 1095 (1.00) \\  & R-\#2 & 9.5 & 1024 (1.05) & 2778 (1.07) & 1141 (1.00) & 1171 (1.07) \\  & R-\#3 & 13.7 & 783 (0.80) & 2377 (0.91) & 1110 (0.97) & 1047 (0.96) \\ \hline \multirow{3}{*}{MSL} & R-\#1 & 7.5 & 1095 (1.00) & 4151 (1.00) & 1730 (1.00) & 1695 (1.00) \\  & R-\#2 & 9.5 & 823 (0.75) & 3793 (0.91) & 1611 (0.93) & 1569 (0.93) \\  & R-\#3 & 13.7 & 627 (0.57) & 2748 (0.66) & 1198 (0.69) & 1191 (0.70) \\ \hline \multirow{3}{*}{LSWL} & R-\#1 & 7.5 & 896 (1.00) & 3738 (1.00) & 1820 (1.00) & 1743 (1.00) \\  & R-\#2 & 9.5 & 717 (0.80) & 2905 (0.78) & 1562 (0.86) & 1549 (0.89) \\ \cline{1-1}  & R-\#3 & 13.7 & 619 (0.69) & 2906 (0.78) & 1287 (0.71) & 1282 (0.74) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Summary of maximum wave forces for real-scale models: \(\mathrm{P_{w}}\) under regular waves.  
Figure 9: Measured wave forces for hybrid under regular waves (**a**) R-#1: HSWL; (**b**) R-#1: LSWL; (**c**) R-#3: HSWL; (**d**) R-#3: LSWL; (**e**) R-#5: HSWL; (**f**) R-#5: LSWL.  
By type of support structure, the variation of the wave force according to the wave period is larger in the monopile and smaller in the GBS and hybrid. With regard to the sea levels, the wave force variation of the monopile is about 0.80 at the HSWL, 0.57 at MSL, and 0.69 at LSWL, and that of the GBS is about 0.91 at HSWL, 0.66 at MSL, and 0.78 at LSWL. In addition, although there is no consistent tendency in the wave force according to the three sea levels for each of the three support structure types, the wave forces in MSL and LSWL are somewhat higher than those in HSWL for the GBS and hybrid. It is considered that the bottom structural members of these two types are composed of a large area and that as the water depth is lowered, these large area members act significantly as a projected area against the wave, as presented in Table 1, resulting in an increased total wave force. However, since the wave height (3.435 m) of this wave condition is not so large, the influence on the wave force is not so large. Judging by the overall trend, it is considered that the nonlinear wave force due to shoaling or diffraction does not occur or its effect is negligible at this wave condition because the wave height (3.435 m) of this wave condition is low.