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Thesis Format

Integrated Article


Master of Engineering Science


Civil and Environmental Engineering


El Damatty, Ashraf A.


Transmission line (TL) structure failures caused by tornadoes have been observed in multiple countries around the globe. The objective of this study is to develop an accurate load case that can simulate the critical tornado forces transmitted from the TL conductors to the towers. In order to achieve the goal, three different tornado wind fields, which were previously developed using computational fluid dynamic simulations, are considered. The tornado wind field provides the most critical forces on the TL conductors is determined and considered to obtain the critical load cases. Using the critical wind field, parametric studies are conducted to identify the tornado position that generates peak longitudinal forces. A parametric study is conducted on two different transmission line systems to assess the influence of conductor parameters on the longitudinal forces. Results of the parametric study are used to develop charts, which together with a three-dimensional interpolation procedure can estimate the critical conductor longitudinal forces on the towers.

Summary for Lay Audience

Tornadoes are rapidly rotating columns of air extending vertically from the surface to the base of a cumuliform cloud. Transmission Lines (TLs) play an important role in transmitting electricity from the source of power to the distributing system. In current days, the reliance of the society on electricity is vital and extended interruption of electricity can cause devastating economic losses and social consequences. Due to the length of TL structures that extends for kilometers, there is a large chance that one of the TL towers gets exposed to the tornado. A large number of TL failures caused by tornadoes have been reported in Canada and worldwide. Triggered by the past failure events, an extensive research program was conducted at the University of Western Ontario to study the behaviour of TLs under tornadoes. The provision for critical tornado load cases that was introduced recently in the American Society of Civil Engineering design guidelines for TL was one of the achievements of this research program. As part of this program, the objective of the current study is to refine these new provisions pertaining to tornadoes by providing accurate means for estimating the loads transferred from the conductors to a TL tower during tornadoes. In order to achieve that, parametric studies are first conducted to analyze the response of TL conductors under different tornadoes. The tornado wind field and its corresponding position that provides the most critical longitudinal forces on the TL conductors are determined. Using these critical tornado configurations, the influence of conductor parameters on the longitudinal forces is then studied. Finally, the results of the parametric study are used to develop a simple and yet accurate approach to calculate the peak conductor longitudinal forces on the towers.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.