Dynamic response and torsional effects of transmission tower-conductor system under translating downbursts: effects of non-orthogonal wind paths

Transmission tower–conductor systems are highly vulnerable to downbursts, whose transient and spatially non-uniform wind fields can induce complex dynamic responses distinct from those generated by synoptic winds. However, existing studies have largely focused on stationary or orthogonal downburst scenarios, while the influence of translating downbursts with oblique motion paths is under-explored. This study addresses this gap by investigating the dynamic response and torsional behavior of a transmission tower–conductor system under translating downbursts with non-orthogonal wind paths. A deterministic–stochastic hybrid model is developed to reproduce the time-varying and non-stationary characteristics of downburst winds. A directional parameter, θ, representing the angle between the downburst translation path and the transmission line orientation, is introduced to evaluate the effects of varying wind directions. The spatially and temporally evolving wind loads are computed along the conductors, and the system’s dynamic responses are analyzed across a range of θ values. Results reveal that translating downbursts induce pronounced spatiotemporal variations in wind loading, leading to substantial unbalanced tensions between adjacent spans. The maximum unbalanced tension occurs at θ = 90°, and decreases with smaller θ. The resulting differential tensions produce significant torsional moments in the tower, which increase and then decrease with θ, peaking at θ = 75°, where the relative torsional angle reaches approximately 1.25°. The maximum tower-top displacement and peak member stress exhibit similar non-monotonic patterns. These findings highlight the critical influence of wind path orientation on tower-line system responses and provide valuable insights for performance-based wind-resistant design of transmission infrastructure.