Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article


Master of Engineering Science


Civil and Environmental Engineering


El Damatty, Ashraf

2nd Supervisor

El Ansary, Ayman



High-intensity wind events (downbursts and tornadoes) cause the majority of weather-related transmission line (TL) failures, which detrimentally affect society. This study investigates the progressive failures of single TL towers and TL systems under different F2 tornadoes. Different tornado wind fields are incorporated in a fluid-structure software developed at Western University. Progressive failure analysis is then conducted for four towers under the most critical tornado configurations identified from extensive parametric studies. Moreover, the cost associated with designing TLs to sustain F2 tornadoes is investigated by strengthening the TL towers. Finally, the progressive failure within self-supported TL systems under different tornadoes, and the effect of changing the insulator length and the TL span on the propagation of failure are examined. To summarize, this thesis compares the progressive failures of TLs under different F2 tornado wind fields. It also presents different techniques to enhance the resilience of TL systems under tornadoes.

Summary for Lay Audience

In Canada, tornadoes occur in almost all southern regions of the country, especially Southwestern Ontario which experiences the highest rate of tornado incidences. Tornadoes are speedily rotating columns of air that extend from the surface of the Earth to the cumulonimbus clouds. Tornadoes are categorized by the Fujita scale. The Fujita scale classifies tornadoes into five categories (F0; least damaging to F5; most damaging) based on the different characteristics of the tornado. This study is motivated by many failure incidences observed in Canada and worldwide of transmission line (TL) systems during tornadoes and by the lack of appropriate design guidelines accounting for high-intensity wind events like tornadoes. The current study is part of a research program initiated at Western University, a few years ago, that focuses on investigating the reasons of failure of TLs under high-intensity wind events and how to improve current design provisions to have more resilient TLs under such extreme wind events. The main objectives of the current study are to investigate the propagation of failure of TL systems under different tornadoes and to examine how changing different components of the TL system affects the failure. The results drawn from the study show that TL towers collapse differently under different tornadoes and that some components of the TL systems significantly affect the resilience of TLs and can be used to mitigate the losses due to tornadoes. To summarize, the thesis presents different approaches to improve the resilience of TLs under F2 tornadoes.