Study on Wind Vibration Response and Coupling Effect of Transmission Tower-Line System Under Downburst

Downburst is a type of near-surface short-term destructive strong wind that significantly affects wind-sensitive flexible structures like transmission tower-line systems. The existence of the tower-line coupling effect complicates the wind-induced vibration response analysis. Firstly, the average wind speed time history is obtained using the impinging jet wind field model, the pulsating wind speed time history is simulated using the harmonic synthesis method, and then the total wind speed time history of the downburst is obtained by superposition. Then, the transmission tower-line finite element model is established to carry out the wind vibration response analysis under different wind attack angles. Based on the most unfavorable wind angle of attack, the wind-induced vibration response and the coupling effect of the tower-line system are investigated under different maximum wind speed heights (Z(max)) and span distances. Finally, the range of wind load reduction coefficients for the tower-line separation system is given. The results show that under the most unfavorable wind angle of attack angle, both the displacement and acceleration response of the tower-line separation system are more significant than that of the tower-line coupling system. At Z(max )= 70m, the difference in displacement response between the two systems reaches the maximum, indicating an apparent tower-line coupling effect. As the span distance increases, both the displacement response and the acceleration response of the tower-line separation system increase. In contrast, the displacement response of the tower-line coupling system increases, but the acceleration response decreases. For the proposed design reduction coefficient for the transmission tower-line coupling effect under the action of the downburst, it is considered more reasonable to take the value between 0.83-0.95. This study provides some references for further optimization of the transmission tower design.