Behaviour and design procedures for transmission towers under high intensity wind loads

点击翻译按钮获取中文摘要

High Intensity Winds (HIW), which include tornadoes and downbursts, are responsible for more than 80% of all the world's weather-related transmission line failures. Despite this fact, the codes of design for transmission lines are based on a conventional wind profile associated with large scale events. HIW have different profiles, which impact the distribution of wind loads over the towers and lines. A research program was conducted at UWO in collaboration with Manitoba Hydro (MH) and other utility companies. A numerical tool was developed to predict the response of transmission lines to HIW. It incorporates wind field simulating HIW obtained from a computational fluid dynamic analysis. Various components of this numerical model were validated separately. The study revealed that structure members located at various regions of a tower can have specific critical HIW characteristics, defined by the size and location of the event, that lead to maximum forces in these members. In the current study, continuous monitoring for the wind velocity and the vibrations of a transmission line system will be conducted. The results will provide more insight about the HIW fields and the response of the towers to those events. They will also be used to validate the entire numerical model. A number of transmission line systems, having various structural configurations, will be numerically modeled. The results will be used to propose a set of design load cases simulating an envelope for the critical HIW cases for various structural systems. An accurate failure model for various components of the transmission lines will be incorporated into the numerical model. This will allow studying the progressive collapse of the towers during HIW. This extended model, together with available climate data for HIW, will lead to the development of a design procedure that will include recommended wind speeds and design load cases. The design procedure will ensure that transmission lines remain undamaged during moderate HIW, while preventing a total collapse during strong HIW. This will help in mitigating the economical and social losses associated with the failures of transmission lines during HIW. Three Ph.D. and two M.Sc. students will be involved in this proposal.