Behaviour of Pre-stressed Concrete Transmission Poles under High Intensity Wind

Among different types of electrical transmission line structures, pre-stressed concrete transmission poles have the advantages of low installation and maintenance costs, appropriate delivery time, and high corrosion resistivity. Typically, these poles are designed to resist synoptic wind loading. Current design codes do not consider the effect of high intensity wind (HIW) events in the form of downbursts and tornadoes on pre-stressed concrete poles despite the fact that those weather events are the main cause of failure of transmission line structures. The first comprehensive study conducted to assess the behaviour of pre-stressed concrete transmission poles under HIW is presented in this thesis. A numerical model is developed and validated incorporating the following: (1) three-dimensional downburst and tornado wind fields previously developed and validated using computational fluid dynamics simulations; (2) an analytical technique previously developed and validated to predict the non-linear behaviour of the transmission line conductors under non-uniform loads resulting HIW events (3) a non-linear finite element model developed in this thesis to simulate the structural behaviour of pre-stressed concrete poles. This numerical model can predict the response of pre-stressed concrete transmission pole structures under downbursts and tornadoes as well as under synoptic wind. The model is then expanded to include the dynamic effects and then used to assess the dynamic response of pre-stressed concrete transmission pole structures to turbulent synoptic wind. The results are used to assess the magnification in straining actions associated with dynamic behaviour as well as the adequacy of the provisions for synoptic wind incorporated in the American Society of Civil Engineers guidelines. Knowing that the turbulence is less significant in HIW compared to synoptic wind, the results of this part of the study provide an upper bound for the dynamic effects associated with downbursts and tornadoes. This upper bound value provides justification for analyzing pre-stressed concrete transmission pole systems under downbursts and tornadoes in a quasi-static manner. Extensive parametric studies are then conducted using the developed numerical model to determine the critical downburst and tornado configurations leading to peak straining actions for a number of guyed pre-stressed concrete pole systems, which are initially designed to remain un-cracked under synoptic wind load. Failure studies are then conducted to assess the downburst and tornado velocities that lead to a full collapse of the poles. The adequacy of load cases recently developed by researchers at the University of Western Ontario to simulate the critical effects of downbursts and tornadoes on lattice steel transmission towers is then assessed for application to pre-stressed concrete pole structures