Finite element modelling of pre-stressed concrete poles under downbursts and tornadoes

Among different types of electrical transmission line structures, pre-stressed concrete transmission poles have the advantages of low installation and maintenance cost, appropriate delivery time, and high corrosion resistivity. Typically, these concrete poles are designed to resist only synoptic wind loading as current codes do not consider high intensity wind events in the form of downbursts and tornadoes. To the best of the authors' knowledge, this study is the first investigation to assess the behaviour of pre-stressed concrete poles under High intensity wind events. Due to the localized nature of those events, identifying the critical locations and parameters leading to peak forces on the poles is a challenging task. To overcome this challenge, a built in-house numerical model is developed incorporating the following: (1) a three-dimensional downburst and tornado wind field previously developed and validated using computational fluid dynamics simulations; (2) A computationally efficient analytical technique previously developed and validated to predict the non-linear behaviour of the conductors under non-uniform loads resulting from those events (3) a non-linear finite element model developed in the current study to simulate the structural behaviour of pre-stressed concrete poles considering material nonlinearity. The non-linear finite element model, is validated using experimental data available in the literature. Extensive parametric studies are conducted using the numerical model to determine the critical downburst and tornado configurations leading to peak overturning moment acting on a pole which is designed to remain un-cracked under synoptic wind load. Failure studies are then conducted to assess the downburst and tornado velocities that would lead to a full collapse of the pole.