Behaviour of Guyed Transmission Line Structures under Tornado Wind Loads—Case Studies

Most wind-related transmission line failures have been attributed to high intensity wind (HIW) events in the form of tornados and downbursts. In the current study, a numerical model is developed to investigate the performance of two guyed transmission lines under tornado wind loads. The F2 tornado wind field used in the study is based on a computational fluid dynamics (CFD) analysis that was developed and validated in previous studies. The tornado wind forces are calculated and are then incorporated into a three-dimensional nonlinear finite-element model that simulates both the towers and the conductors. The study investigates the effect of tornado loads on the structural performance of the two different guyed transmission line systems. The tornado locations leading to maximum internal forces in various members of the towers are identified and are considered as critical load cases. The nonlinear numerical model is then extended to study the progressive failure of the two transmission lines under the critical tornado load cases by varying the velocity of the tornado wind fields incrementally. The velocities at which a total collapse is predicted are identified for both towers.