Performance-Based Design of Transmission Line Structures Under Tornadoes and Downbursts

暴雨和龙卷风属于一种被称为高强度风（HIW）的风暴。本文的研究重点是这些极端事件对输电线路结构的影响。在加拿大和其他国家，每年都观察到这些结构在高强度爆炸事件期间发生的故障事件，造成巨大的经济损失。在风对建筑物的影响研究方面，西方大学一直处于领先地位。它的研究能力通过建立WindEEE圆顶而得到增强，这是一个价值3000万美元的设施，代表了世界上第一个在大规模HIW下测试结构的室。HIW场由平均和湍流组成，两者都取决于场地地形是开放的、郊区的还是城市的。在他之前的DG中，申请人关注的是在开阔地形下HIW场的平均分量对tl的影响。随着WindEEE的HIW现场数据的可用性，研究将进入更高的水平。利用不同地形对应的HIW场对tl进行数值模拟，同时改变事件的位置。将确定导致塔楼成员力量达到峰值的关键位置。分析将考虑湍流引起的动力效应。结果将采用荷载案例的形式，模拟各种地形条件下HIWs平均分量的关键影响，以及将这些荷载放大的阵风响应因子，以解释动态影响。当输电塔倒塌时，连接导体的分离会导致产生不平衡的纵向力，作用在后续的塔上，造成一系列的塔故障。将开发一种新的非线性数值模型来模拟整个线路系统的逐步崩溃，该模型将通过在windee进行的测试进行实验验证。得益于大型风力测试设施的可用性，该实验项目将把风力测试带到失效调查的新视野。由于TL延伸数百公里，因此设计一条线路的所有塔在极端HIW事件下保持不损坏可能是非常昂贵和不切实际的。一个基于性能的设计程序将在本提案中描述。期望的性能标准将包括由于部分线路故障而造成的影响和电力中断的持续时间的最小化，以及对这种故障的遏制。这项研究将为一个全球性问题找到可持续的解决方案，将为风荷载下基于性能的结构设计建立一个框架，并将为6名研究生提供最新的数值和实验技术培训，这将解决一个非常实际和紧迫的问题。

Downbursts and tornadoes belong to a category of storms that are referred to as High Intensity Winds (HIW). The proposed research focuses on the effect of these extreme events on transmission line (TL) structures. Failure incidents of those structures during HIW events have been observed on an annual basis in Canada and amongst other countries, resulting in huge economic losses. Western has consistently taken the lead in research related to the effect of wind on structures. Its research capabilities have been augmented by the establishment of the WindEEE dome, a $30M facility representing the first chamber in the world for testing structures under large scale HIW. The HIW fields consist of a mean and a turbulent component, which are both dependent on whether the site terrain is open, suburban or urban. In his previous DG, the applicant focused on the effect of the mean component of the HIW fields on TLs in the case of open terrain. With the availability of HIW field data from the WindEEE, the research will be taken to a higher level. Numerical simulations will be conducted for TLs using HIW fields corresponding to different terrains, while varying the location of the event. Critical locations leading to peak forces in the tower members will be identified. The analyses will be conducted considering the dynamic effects resulting from turbulence. The outcome will take the form of load cases simulating the critical effects of the mean component of HIWs for various terrain conditions, together with gust response factors magnifying these loads to account for dynamic effects. When a transmission tower collapses, the de-attachment of the connected conductors leads to the creation of unbalanced longitudinal forces acting on subsequent towers causing a chain of tower failures. A novel nonlinear numerical model will be developed to simulate the progressive collapse of an entire line system, which will be validated experimentally through tests conducted at WindEEE. This experimental program will take wind testing to new horizons for failure investigation, benefiting from the availability of a large scale wind testing facility. Since a TL extends for hundreds of kilometers, it could be very expensive and impractical to design all the towers of a line to remain undamaged under extreme HIW events. A performance-based design procedure will be developed as described in this proposal. The desired performance criteria will involve the minimization of the effect and the duration of the interruption of electricity due to the failure of a portion of the line as well as the containment of such a failure. The research will lead to finding a sustainable solution to a worldwide problem, will set up a framework for a performance-based design of structures under wind loading, and will provide training for 6 graduate students in state-of-theart numerical and experimental techniques, which will address a very practical and pressing problem.