Introduction: With the sustainable growth in electricity demand, an increasing number of transmission lines must traverse high-seismic-intensity mountainous regions. Due to topographic heterogeneity, uneven horizontal span distribution, and elevation differences between transmission towers are common in mountainous areas. This paper investigates the dynamic response of a transmission tower-line system under seismic loads, focusing on the effects of the uneven distribution of horizontal spans and elevation variations. Finite element models of the transmission tower-- line system were developed utilizing ABAQUS software. Three ground motion records were selected from the PEER database and applied at the base of the tower legs in the direction perpendicular to the conductor. The span unevenness coefficient, Φ, and the elevation variation coefficient α, were then proposed. By comparing the stresses of four observed members and the displacements at observed points under different working conditions, this study investigates the effects of the uneven distribution of horizontal spans and elevation variations on the seismic responses of the transmission tower-line system. Methods: To investigate the influence of complex terrain on the dynamic characteristics of transmission tower-line systems, a series of nonlinear time-history analyses was conducted using three different seismic waves. A parametric study was implemented by varying the span unevenness coefficient (Φ) from 1.000 to 1.439 and the elevation variation coefficient (α) of the middle tower from 0 to 0.286. These parameters were utilized to evaluate the sensitivity of maximum member stresses and nodal displacements to topographic irregularities and span configurations. Results: When horizontal spans are unevenly distributed and elevations vary between adjacent transmission towers, the resulting alteration in the conductor sag profile leads to an uneven tension distribution, thereby increasing the seismic response. Discussion: Therefore, in the seismic design of transmission towers located in high mountainous regions, it is crucial to consider the amplification effects caused by both uneven horizontal span distribution and elevation variation. Conclusion: This research provides a reference for the seismic design of transmission towers in mountainous terrains, which can also contribute to the development of innovative engineering solutions with potential patent applications.
Liu et al. (Wed,) studied this question.