###### Abstract
[20] used tensioned joint reliability to estimate the reliability of slender steel lattice telecommunication towers by a full-scaled pushover test of a 40 m tall lattice tower. Several codes, standards and design provisions have proposed simplified static methods for the seismic estimation for transmission steel towers [21; 22; 23], but none of the norms have suggested using the non-linear dynamic analysis (NL-DA) approach. This provision demonstrates the gaps and limitations in estimating seismic design capability. Furthermore, since the transmission lines spans are large in modern civil engineering construction, the effects of multiple excitations must be carefully considered, and the frequent failures of transmission line tower systems show that the load pattern defined in the codes does not accurately reflect realistic load conditions [24]. Due to the aforementioned limitation gap in the proposed provisions, this research is undertaken to conduct a non-linear dynamic analysis to understand and estimate the load pattern in transmission line towers. A non-linear time history analysis (NL-THA) technique is used to estimate the tower Collapse Margin Ratio (CMR) and the probability of damages is calculated using vulnerability functions. The CMR was originally proposed by FEMA P-695, as one of the best structural collapse indicators established in the last decade [25]. According to FEMA P-695, various factors influence the CMR, including ground motion variability and uncertainty in the structure's design, analysis, and construction. These variables are combined in a collapse fragility curve, which describes the likelihood of the seismic-force-resisting system collapsing as a function of ground motion intensity related to FEMA P-695 [26]. The CMR is an effective tool for determining the capability of a structure to withstand structural collapse. Thirty-six ground motion records comprising 18 far-field (FF) and 18 near-field (NF) earthquakes are used to simulate two types of earthquakes that have different characteristics and involve different behaviours in structures [27]. Near-field earthquakes occur in fieldsclose to the fault, while far-field earthquakes occur in fields far from the fault. For instance, some researchers propose a near-field range of 10 to 60 km around the fault [28]. On the other hand, some international code standards define the site-to-source distance less than 15 km as the near-field, while the far-field range can be described as a distance greater than 15 km from the epicentre of an earthquake. The properties of far-field ground motions are different from near-field ground motions. When compared to higher frequencies of far-field ground motions, near-field ground motions have higher acceleration and more restricted frequency range [28]. Furthermore, far-field ground motion is less disruptive and devastating than near-field ground motion [29]. This could imply that far-fault ground motions are less likely than near-field ground motions to cause transmission steel tower failure or even collapse. Consequently, it is critical to assess the vulnerability of transmission steel towers in both far-field and near-field ground motions, in order to reduce the risk of tower failure or collapse during an earthquake and keep the tower operational after the event. Furthermore, the collapse of a tower can be avoided by ensuring better seismic code compliance in new constructions and rehabilitating existing structures. To date, there have been few studies that have evaluated the vulnerability of lattice transmission steel towers under the influence of the Far-Field (FF), Near-Field (NF), and repeated ground motions. In this study, the seismic performance of a steel transmission tower is evaluated for three different seismic scenarios; such analysis will be useful in updating the code regulations and demonstrating that it is dangerous to ignore seismic effects on transmission towers.