Abstract
Disaster investigation results have shown that most wind-induced damage to transmission towers is related to downbursts. To clarify the effects of downbursts’ parameters on transmission towers with different heights, studies were conducted on five transmission towers with different diameters under static and moving downburst wind conditions. As a comparison, the responses of the towers under normal wind conditions were studied. The results showed that the effect of downbursts on the response of the transmission tower increased with the distance between the downburst center and the tower (r) when r < 1.0 Djet (Djet is the jet diameter of downburst) and then decreased when r > 1.0 Djet. The effects of jet diameter on the response of transmission towers with different tower heights were similar. As the jet diameter increased, the response of the tower continued growing until it reached a peak value and then steadily decreased soon thereafter. When the tower height was below 81.5 m, the wind load of the downburst on the transmission tower was significantly greater than that of the normal wind. As the tower height increased, the ratio of the transmission tower’s response under the two types of wind fields rapidly declined to about 0.91–1.01.
Highlights
Comparing the main material’s axial force of the 45.5–72.5 m tower under the two types of wind fields, we found that the axial force generated by the downburst was greater than the boundary layer wind, which had a greater effect on the wind load of the transmission tower
Based on the above analysis results, the following conclusions can be drawn: (1) When the transmission tower was located near r = 0.9–1.0 Djet, the impact of the downburst wind load was the greatest
When r/Djet = 1.0, the most unfavorable jet diameters corresponding to towers with H = 45.5, 54.5, 63.5, 72.5 and 81.5 m were 900, 1100, 1300, 1400 and 1600 m, respectively
Summary
Shehata [10,11,12] introduced a finite element model for whole-guyed transmission lines under downburst and provided a reference for the wind load design of transmission towers They studied the structural behavior of a tower in the most unfavorable conditions by changing the wind field of the downburst. Elawady [18,19] conducted aeroelasticity tests on multispan transmission lines under the downburst in the WindEEE dome, which showed very good agreement between the critical configurations of the downburst obtained from the experiment compared with those predicted previously by different numerical studies These studies have focused mainly on response analysis, stability research, and collapse and failure process of a specific transmission tower, but rarely have they involved the influence of structural parameters.
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