Localized wind events in the form of tornadoes and downbursts are the main cause of the large number of failure incidents of electrical transmission line structures worldwide. In this study, numerical models are developed to study the behaviour of one self-supported and one guyed transmission lines under various tornado events. The tornado wind fields used are based on a full three-dimensional computational fluid dynamics analysis that was developed in an earlier study. Three-dimensional finite element models of existing transmission lines belonging to a hydro utility company are developed. The models are used to assess the lines' failure mechanisms under critical tornado configurations. A nonlinear progressive failure analysis is conducted for each transmission line. Each analysis is conducted by carrying out numerical iterations during which various members progressively fail until global failure is reached and the tower of interest collapses. The study predicts the progressive failure mechanism of the modeled transmission lines as well as the maximum tornado velocity the various lines can withstand before experiencing global failure. The study also predicts the main type of failure experienced as well as the path of members susceptible to failure. This could then be used to retrofit existing transmission lines economically by increasing the capacity of the identified members.
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