Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Civil and Environmental Engineering


Dr. Ashraf El Damatty


During the past years, many electrical transmission lines have failed during downbursts. This thesis is part of a research program aimed to understand the behaviour of transmission lines under localized winds. The first part of the thesis assesses the dynamic behaviour of the conductors under downburst loading. A non-linear numerical model is utilized to predict the natural frequencies and mode shapes of the conductors at various loading stages. A turbulence signal is added to the mean component of the downburst wind field previously evaluated from a CFD analysis. Dynamic analysis is performed using various downburst configurations.

The second part of the thesis focuses on evaluating the sensitivity of the forces in the members of guyed towers to changes in the downburst configuration, tower height, guys’ configuration, turbulence, and the conductors’ pretensioning force. The axial forces in the members are compared to those resulting from normal wind loading and the broken wire load case.

The third part of the thesis focuses on developing simplified loads, equivalent to the critical downburst loads causing the guyed transmission tower to fail. Different options are considered in terms of the location and nature of the design velocity associated to different critical cases. The profile of the horizontal velocity is developed. The equivalent load corresponding to each of the critical cases is developed. Detailed steps of the conductors’ reactions calculations are provided. A loading procedure is developed for designing downburst loaded guyed transmission towers.


The fourth part of the thesis involves studying the behaviour of self supported transmission line towers under downburst loading. A parametric study is performed to determine the critical downburst configurations causing maximum axial forces for various members of the tower. The sensitivity of the internal forces developing in the tower’s members to changes in the downburst size and location is studied. The structural behaviour associated with the critical downburst configurations is described and compared to the behaviour under normal wind loads.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.