Finite element modeling of transmission line under downburst wind loading

Abstract

Despite the fact that extensive research has been carried out on transmission lines subjected to normal wind loads, their behaviour under high intensity wind loads (HIW), such as downburst, is poorly defined. This paper describes a detailed numerical model that can be used to predict the structural performance of a transmission towers as part of a transmission line system under downburst loading. The time history of the downburst wind data is based on a previously developed and validated computational fluid dynamic model. The procedure used to scale the velocity wind data and to transform them to forces is described. Three-dimensional linear elastic frame elements are used to model the members of the towers while two-dimensional curved beam elements with geometric non-linearity included are used to model the conductors and the ground wires. A transmission line that suffered previously from significant damage due to a downburst event is then considered as a case study. Comparison between the results of the downburst analysis and those due to a normal wind that are typically used in the design reveals the importance of considering HIW loads when attempting the structural design of transmission towers.