# Study on Wind Resistance Performance of Transmission Tower Using Fixture-Type Reinforcement Device
## 3 Transmission Tower and Wind Load
### Wind Load  
The Chinese standard load code for the design of overhead transmission Lines [25] gives specifications on how to calculate the wind load taken by the tower structure and  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**No.** & **Shape** & **Specification** & \
\begin{tabular}{c} **Length of** \\ **Wing (mm)** \\ \end{tabular} &
\begin{tabular}{c} **Thickness of** \\ **Wing (mm)** \\ \end{tabular} \\ \hline
1 & L & 50 \(\times\) 5 & 50 & 5 \\
2 & L & 50 \(\times\) 4 & 50 & 4 \\
3 & L & 45 \(\times\) 4 & 45 & 4 \\
4 & L & 80 \(\times\) 6 & 80 & 6 \\
5 & L & 63 \(\times\) 5 & 63 & 5 \\
6 & L & 40 \(\times\) 3 & 40 & 3 \\
7 & L & 75 \(\times\) 5 & 75 & 5 \\
8 & L & 70 \(\times\) 5 & 70 & 5 \\
9 & L & 56 \(\times\) 5 & 56 & 5 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Dimensional data for angled steel components of the transmission tower.  
Figure 6: Vibration modes of the transmission tower: (**a**) 1 st order; (**b**) 2 nd order; (**c**) 3 rd order; (**d**) 4 th order; (**e**) 5 th order.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Order** & **Vibration Mode** & **Frequency (Hz)** \\ \hline
1 & Bending around y-axis & 1.575 \\
2 & Bending around x-axis & 1.577 \\
3 & Bending around y-axis & 6.832 \\
4 & Bending around x-axis & 6.983 \\
5 & Torsion around z-axis & 8.711 \\ \hline \hline \end{tabular}
\end{table}
Table 5: First five vibration modes and frequencies of the tower structure.  
grounding cables. The wind load on the transmission tower structure can be calculated by the following equation:  
\[W_{s}=W_{0}\cdot\mu_{z}\cdot\mu_{s}\cdot\beta_{z}\cdot B_{2}\cdot A_{s} \tag{1}\]  
where \(W_{s}\) is the wind pressure taken by the component of the transmission tower structure; \(W_{0}\) is the reference wind pressure of a certain area, and can be derived from appendix; \(\mu_{z}\) is the height variation coefficient of wind pressure, which accounts for the influence of elevation; \(\mu_{s}\) is the shape coefficient of the component; \(\beta_{z}\) is the wind fluttering coefficient at the height of \(z\); \(B_{2}\) is the amplification coefficient of the component when it is covered by ice; and \(A_{s}\) is the projected area of the component.  
The wind pressure exerted on the transmission cables and grounding cables can be calculated by Equation (2)  
\[W_{x}=\beta_{c}\cdot\alpha_{L}\cdot W_{0}\cdot\mu_{z}\cdot\mu_{sc}\cdot d\cdot L _{p}\cdot B_{1}\cdot\sin^{2}\theta \tag{2}\]  
where \(\beta_{c}\) is the gustiness factor of the transmission or grounding cable; \(\alpha_{L}\) is the span reduction factor; \(\mu_{sc}\) is the shape coefficient of the cable; \(d\) is the outer diameter of the cable; \(L_{p}\) is the horizontal span between towers; \(B_{1}\) is the amplification coefficient of the cable when covered by ice; and \(\theta\) is the angle between the direction of the wind and that of the cable.  
Considering the velocity of the wind, the wind load of the tower and the cables can be derived based on Equations (1) and (2), and they are directly applied to the finite element model as the static loads. Two directions of the wind load are taken in the analysis: (1) along the direction of the transmission cables and (2) perpendicular to the direction of the transmission cables. Here, it should be noted that the two directions can form the plane parallel to the horizontal plane, as illustrated in Figure 7.