## 3 Results and Discussion  
### Incremental Dynamic Analysis (IDA)  
It is critical to understand the structural performance of transmission steel tower line systems during a variety of ground motions. Incremental dynamic analysis is a quantitative technique that is used to evaluate the important elements that control structural performance and its seismic capacity based on the performance limit states provided by FEMA 356 and recommended by the Performance-Based Earthquake Engineering (PBEE) framework. In this reported work, a simulation of Strong Ground Motions (SGM) is carried out to predict the seismic performance of a structure utilising an array and variety of \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Number of Mode**} & \multirow{2}{*}{**Natural Period (s)**} & \multicolumn{2}{c}{**Natural Frequency**} & \multirow{2}{*}{**Deformed Shape**} \\  & & **(Hz)** & & \\ \hline
**1** & 1.061 & 0.942 & Translating in \(Y\)-axis (Longitudinal) \\
**2** & 0.789 & 1.267 & Translating in \(X\)-axis (Transversal) \\
**3** & 0.651 & 1.536 & Rotating about \(Z\)-axis (Torsion) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Natural Period and frequency of the first three mode deforming shapes. Figure 11: Mode shape for transmission steel tower, (**a**): 1 st Mode shape, (**b**): 2 nd Mode shape, and (**c**): 3 rd Mode shape. ground motion records relating to far-field earthquakes as well as near-field and repetitive earthquakes. The IDA curves are plotted with the IM of the Sa(T1, g) against the EDP of the ISDR in order to provide an overview of the seismic performance of the tower under three seismic scenarios (far-field, near-field, and repetitive) ground motions until collapse point is reached as shown in Figure 12.  
The overall seismic capability performance towards the tower is similar for the three seismic scenarios at the IO performance level, implying that the tower retains much of its original strength and stiffness. This, in turn, means that the tower is in continuous service with negligible tower damage. There may be minor cracking in the structural frame elements of the tower. The far-field ground motion requires 0.25 g while near-field and repetitive ground motions require 0.20 g and 0.196 g, respectively, to reach the IO performance level. Furthermore, in order to achieve the LS performance level, the far-field, near-field, and repetitive ground motions required 0.80 g, 0.60 g, and 0.57 g as the mean of  
Figure 12: IDA curves for three seismic scenarios; (**a**): Far-Field, (**b**): Near-Field, and (**c**): Repetitive earthquakes. mainshock and aftershock, respectively. In this level, the tower sustains severe damage, but there is still some safety from a catastrophic tower collapse, resulting in moderate overall damage. A certain amount of residual strength and stiffness continue to remain in all tower levels, causing serious damage to a few tower frame components, although this may not create substantial falling debris risks, either inside or outside the tower. Moreover, at the CP performance level, the far-field, near-field, and repetitive seismic scenarios require 1.10 g, 0.80 g, and 0.78 g, respectively. The tower is at the point of total collapse due to considerable degradation in the strength and stiffness of the lateral-force-resisting system and massive permanent lateral deformation of the structure. As a result, it's possible that the tower may not be repairable and may not be safe to rebuild.