###### Abstract  
Transmission towers are a vital lifeline for modern living and are crucial structures that must remain operational even after a seismic event. However, the towers are largely designed to withstand the effects of wind alone and not earthquakes, and the seismic influences on tower design and construction have hitherto been ignored. The purpose of this study was to evaluate the seismic performance of a latticed steel transmission tower-line system that is subjected to a variety of seismic situations (Far-Field, Near-Field and Repeated Earthquakes) using probabilistic vulnerability functions and Collapse Margin Ratios in accordance with FEMA-P695. Nonlinear Time History Analyses were performed by incorporating an array of 36 strong ground motions to develop the Incremental Dynamic Analysis and to generate the fragility functions for three performance limit states as referenced in FEMA 356. The results showed that the single event seismic performance of the tower is better than its performance after multiple ground motions owing to aftershock impact, while near-field excitations led to greater susceptibility and fragility than far-field scenarios. Thus, near-field ground motion is more harmful to the tower and could result in its failure or collapse with only a small reduction in damage relative to the impact of the aftershock. repeated earthquakes; vulnerability function; collapse margin ratio; incremental dynamic analysis; fragility curve +
Footnote †: journal: Applied Sciences  
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M.M.K.M. systems. A total of 69 transmission lines were destroyed, 15 transmission towers collapsed, and 26 transmission towers tilted. The Wenchuan earthquake of 2008 in China caused the collapse of more than 20 transmission towers in the Mao County area, as well as the destruction of a 220 kV transmission line in the region [5; 6; 7]. The Kocaeli earthquake in Turkey in 1999 induced landslides, faulting, and surface ruptures, thus damaging many of the transmission towers [4]. Figure 1 shows the collapsed transmission towers caused by the Wenchuan earthquake in 2008. The transmission steel tower is typically designed by considering the wind effects as the primary source of the lateral loads with no attention paid to seismic effects. This is because wind lateral loads are thought to be much greater than seismic lateral loads on high-rise transmission towers, particularly in open areas. However, earthquake effects on towers may be more severe than wind effects and seismic lateral load cannot be ignored, particularly in high-seismic zones, because seismic lateral loads can also cause significant damage to the transmission and telecommunication steel towers. Thus, design checks, even if simple ones, must be incorporated to account for seismic-event induced lateral load [8]. It is also imperative to perform a vulnerability assessment on transmission steel towers that have been subjected to earthquakes. There have been few studies on the evaluation of earthquake-related tower performance [9; 10; 11; 12; 13; 14; 15]. [PERSON] et al. [16] used static equivalent and dynamic time history methods to compare the structural response of a self-supported communication tower in terms of internal forces and displacements under hurricane wind conditions. [PERSON] [17] studied the effect of soil type on seismic response of the stiff and ductile part of tall telecommunication towers with random vibration analysis. In the modelling and analysis, various conditions of the soil under the tower and various damping conditions were used. [PERSON], et al. [18] proposed using structural topology optimization to develop solutions for lattice self-supported telecommunication towers in terms of weight-to-stiffness ratio. [PERSON] and [PERSON] [19] presented a comparative study of self-supporting telecommunication towers using dynamic analysis for optimum modal combination and discretization. [PERSON] et al.