Failure Analysis of Transmission Towers subject to Downbursts

摘要

The occurrence of severe wind downburst events may lead to the failure of latticedrnelectricity transmission towers. The wind profiles and failure modes due to therndownburst are different from those due to boundary layer winds. In this paper, therndesign wind loads for downbursts are proposed, and a novel analytical framework isrnformulated for checking the section wind-resistance capability under downbursts. Inrnthe framework, the bending moments on the bottom section of a tower induced byrndownbursts are considered to be equal to each other, and on the basis of this therndamage zones and their heights along the tower under downbursts are determinedrnand the corresponding wind-resistance capability is then calculated. The effects ofrnnon-linear deformations of transmission lines in catenary due to downbursts arernconsidered in the framework. It is found that the peak values of the section momentsrnexceed the ultimate section moment capability over about a third of the tower heightrnunder downbursts, while failure occurs in the bottom panel of the tower underrnboundary layer winds. This is consistent with results of the field investigations.