## 4 Results
### Environmental Load Scenarios  
The envelopes of maximum shear forces and bending moments obtained for the four environmental load scenarios are presented in Figure 5. Each color corresponds to a different load scenario, while the line type denotes the structural model. The influence of wave loads on the distribution of shear forces can easily be seen by comparing these results with the those for the wind-only loads (Figure 3). Near sea level, the shear forces  
Figure 4: Maximum shear forces and bending moments at mudline level due to wind-only scenarios. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Wind velocity** (m/s) & **5** & **10** & **15** & **20** & **25** \\ \hline \multirow{3}{*}{Normal Turbulence Model (NTM)} & Simplified Model & 97.18 & 380.74 & 310.65 & 249.44 & 221.45 \\  & OpenFAST & 109.36 & 450.75 & 341.94 & 221.68 & 246.11 \\  & Difference (\%) & 11.13 & 15.53 & 9.15 & \(-12.52\) & 10.02 \\ \hline \multirow{3}{*}{Extreme Turbulence Model (ETM)} & Simplified Model & 142.42 & 474.10 & 357.38 & 272.92 & 234.08 \\  & OpenFAST & 179.81 & 505.19 & 467.29 & 269.60 & 260.58 \\  & Difference (\%) & 20.79 & 6.15 & 23.52 & \(-1.23\) & 10.17 \\ \hline \multirow{3}{*}{Extreme Operating Gust (EOG)} & Simplified Model & 483.15 & 960.42 & 573.68 & 381.10 & 297.16 \\  & OpenFAST & 214.26 & 438.00 & 446.35 & 386.78 & 341.21 \\ \cline{1-1}  & Difference (\%) & \(-125.50\) & \(-119.27\) & \(-28.53\) & 1.47 & 12.91 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Maximum bending moments in MN m at mudline level due to wind-only scenarios. rapidly increases with depth due to the action of wave loads. This increment is reduced for points near the mudline level as the wave loads vanish. On the contrary, wind loads mainly govern the bending moments of the structure, which almost linearly increase from the hub height to the seabed. The two structural models present similar distributions of internal forces, but their values differ depending on the case. Again, the largest differences are found for the load case that involves the extreme operating gust at the rated wind velocity (E-3), and the simplified model overestimates the results of OpenFAST, especially in terms of bending moments. For the rest of the environmental load scenarios, a fairly good agreement is found in terms of bending moments. The maximum shear forces and bending moments at the transition piece and mudline level due to the environmental load scenarios are presented in Tables 9 and 10, respectively, to quantify the relative difference between the two models. Figure 6 also presents these values for a visual comparison. It is clearly seen that the system response in scenario E-3 is substantially higher in the simplified model than in OpenFAST. This overestimation is consistent with the conclusions presented by [PERSON] et al. [16], which is attributed to the conservative approach for the load combination proposed by [PERSON] et al. [6]. Also, another main difference between the two models is the fact that dynamic effects are not considered in the simplified model, apart from for the DAF wave load amplification. Dynamic effects, such as aeroelastic damping, are especially relevant in the E-3 scenario, for which the wind load presents high variability. In the context of shear forces at the transition piece and mudline level due to environmental load scenarios, the data reveal a variance between the simplified and OpenFAST models. For instance, at the transition piece level, the simplified model predicts a shear  
Figure 5: Envelopes of maximum shear forces and bending moments along the structure due to environmental load scenarios.