# Seismic Effect of Marine Corrosion and CFRP Reinforcement on Wind Turbine Tower
## 3 Numerical Analysis of Seismic Dynamic Response
### Influence of Earthquake Types and PGA  
The displacement time history curves of the top of the wind turbine tower structure under different earthquake actions are extracted, as shown in Figure 8. It can be clearly seen from Figure 8 that under the action of the El Centro earthquake, when PGA = 0.07 g, the maximum displacement at the top of the wind turbine tower appears at 12.79 s, the maximum value is 0.051 m; when PGA = 0.2 g, the maximum displacement at the top of the wind turbine tower appears at 6.02 s, the maximum value is 0.122 m; when PGA = 0.4 g, the maximum displacement at the top of the wind turbine tower appears at 6.02 s, the maximum value is 0.245 m.  
Under the action of Nihonkai-Chubu earthquake, the time history curve of tower top is shown in Figure 9. When PGA = 0.07 g, the maximum displacement of the top of the wind turbine tower appears in 41.55 s, the maximum value is 0.211 m; when PGA = 0.2 g, the maximum displacement of the top of the wind turbine tower appears in 41.59 s, the maximum value is 0.493 m; when PGA = 0.4 g, the maximum displacement of the top of the wind turbine tower appears in 41.56 s, the maximum value is 0.989 m.  
Under the action of the Hyogoken-Nanbu earthquake, the time history curve of tower top is shown in Figure 10. When PGA = 0.07 g, the maximum displacement of the top of the wind turbine tower appears at 11.04 s, the maximum value is 0.031 m; when PGA = 0.2 g, the maximum displacement of the top of the wind turbine tower appears at 11.04 s, the maximum value is 0.085 m; when PGA = 0.4 g, the maximum displacement of the top of the wind turbine tower appears at 11.03 s, the maximum value is 0.170 m. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Earthquake** & **Station Location** & **Fault Distance (km)** & **PGA (cm/s2)** & **PGV/PGA (s)** & **ML** \\ \hline El Centro & El Centro#9 & 6.09 & 341.7 & 0.10 & 6.9 \\ Nihonkai-Chubu & Akita meteorological station & 14.0 & 58.6 & - & 7.7 \\ Hyogoken-Nanbu & Takarazuka & 16.1 & 818.0 & 0.12 & 7.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The characteristics of different earthquake records. Comparing the above results, it can be seen that the time of maximum displacement of the structure under the El Centro earthquake has changed, but the maximum displacement of the structure under the other two types of earthquakes has not changed, as shown in Figure 11a. In addition, the maximum displacement of the structure increases significantly under the far-field earthquake, which shows that the displacement caused by the far-field earthquake is more obvious for the structure with a longer natural vibration period. When PGA increases from 0.07 g to 0.2 gal, the maximum displacement of the El Centro earthquake and the Nihonkai-Chubu earthquake increases by 136% and 135%, respectively, and the maximum displacement of the tower increases by 174%, respectively, under the Hyogoken-Nanbu earthquake. Similarly, when PGA increases from 0.2 g to 0.4 g, the maximum displacement of the tower increases by 136% and 135%, respectively. The maximum displacement of the structure under the Hyogoken-Nanbu earthquake is 448% higher than that under the 0.07 g earthquake, which is significantly larger than that under the other two kinds of earthquakes. The structural dynamic response changes under  
Figure 8: El Centro earthquake. Figure 9: Nihonkai-Chubu earthquake. different earthquake records are shown in Table 5. Therefore, it can be seen that the displacement response of the structure under the near-field earthquake is larger. The peak acceleration at the top of the structure under three kinds of earthquake action can be seen from Figure 11b. Under the action of the Nihonkai-Chubu earthquake, the structural acceleration is obviously larger than that of the other two kinds of earthquake. However, the increment of peak acceleration with PGA under the El Centro earthquake and the Hyogoken-Nanbu earthquake is larger than the peak acceleration under the Nihonkai-Chubu earthquake.