# Seismic Effect of Marine Corrosion and CFRP Reinforcement on Wind Turbine Tower
## 3 Numerical Analysis of Seismic Dynamic Response
### Affect of CFRP Reinforcement on Seismic Performance of Wind Turbine Tower  
Take the wind power tower that has been corroded for 30 years as an example. The corrosion section of the wind power tower is reinforced with CFRP as shown in Figure 19. The CFRP model is created using the S4R unit in the ABAQUS2020 software. Use Create Composite Layup to set the number of fiber layers, the thickness of each fiber layer, and the ply angle of each fiber layer. The material properties of CFRP are expressed by the \"ENGINEERING CONSTANTS\" model and the \"HASHIN DAMAGE\" model. The CFRP material parameters are shown in Table 6.  
The reinforcement height is 12 m. The number of CFRP layers is divided into two layers, four layers and eight layers. The CFRP laying direction is \(0^{\circ}\) and \(90^{\circ}\), alternately. In order to make the structural damage more obvious, the Nihonkai-Chubu earthquake, with a smaller predominant frequency, was selected for loading. In order to fully develop the plasticity of the structure under earthquake action, the seismic peak acceleration is adjusted to 2G during loading.  
Figure 18: Moment Curvature hysteretic curve of structure under earthquake action: (**a**) Without corrosion; (**b**) 10 years of corrosion; (**c**) 20 years of corrosion; (**d**) 30 years of corrosion.  
The displacement time history curve of the tower top and the residual deformation curve of the structure after the earthquake are shown in Figure 20. The influence of CFRP reinforcement on the displacement response of the structure on the second and fourth layers is similar. Compared with the reinforced structure, the displacement extreme value is reduced from 4.013 m to 3.687 m and 3.688 m, and the residual deformation of the tower top is reduced from 0.091 m to 0.067 m and 0.068 m. The reinforcement effect of 8-storey CFRP is more obvious than that of two-layer and four-layer reinforcement. The maximum displacement of the structure is reduced to 3.527 m, a decrease of 12.1%, and the residual displacement of the top is reduced to 0.014, a decrease of 8.5%. From the residual deformation of the structure along the tower height after the earthquake in Figure 20d, it can be seen that the residual deformation in the CFRP reinforced area is significantly reduced, and the effect of the eight layers of CFRP reinforcement is the most significant, which can reduce the structural corrosion area and the deformation of the tower top.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameters** & **Values** & **Parameters** & **Values** \\ \hline E\({}_{1}\)/GPa & 235 & X\({}_{\text{T}}\)/MPa & 3400 \\ E\({}_{2}\)/GPa & 17 & X\({}_{\text{C}}\)/MPa & 1700 \\ \(\
u_{12}\) & 0.34 & Y\({}_{\text{T}}\)/MPa & 62 \\ G\({}_{12}\)/GPa & 48 & Y\({}_{\text{C}}\)/MPa & 190 \\ G\({}_{13}\)/GPa & 48 & S\({}_{\text{XY}}\)/MPa & 81 \\ G\({}_{23}\)/GPa & 45 & S\({}_{\text{YZ}}\)/MPa & 81 \\ \hline \hline \end{tabular}
\end{table}
Table 6: CFRP material parameters.  
Figure 19: Wind turbine tower strengthened with CFRP.  
Figure 20: _Cont._  
It can be seen from Figure 21 that the main damage position of the structure that only strengthens the corrosion area is the upper tower, especially the top of the tower. This can also be obtained from the residual deformation of the structure. With the increase of CFRP layers, the damage degree of the steel pipe pile at the bottom of a wind power tower tends to increase.