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

下击暴流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，每年都会观察到这些结构在HIW事件期间的失效事件，造成巨大的经济损失。在与风对结构的影响相关的研究中，WESTERN一直处于领先地位。它的研究能力随着WindEEE穹顶的建立而得到增强，这是一个耗资3000万美元的设施，代表着世界上第一个用于测试大规模HIW下结构的试验室。HIW场由平均值和湍流分量组成，这两个分量都取决于场地地形是开阔的、郊区的还是城市的。申请人在其以前的副秘书长一书中重点讨论了在开阔地形的情况下，高强度加权平均分量对TLS的影响。随着来自WindEEE的HIW现场数据的获得，这项研究将被提高到一个更高的水平。将使用对应于不同地形的HIW场对TL进行数值模拟，同时改变事件的位置。将确定导致塔架构件力量达到峰值的关键位置。分析将考虑湍流产生的动力效应。结果将采用模拟不同地形条件下HIW平均分量的临界影响的载荷情况的形式，以及放大这些载荷的阵风响应系数来考虑动态影响。当输电铁塔倒塌时，连接的导线的分离会导致作用在后续铁塔上的不平衡纵向力，从而导致一连串的铁塔故障。将开发一种新的非线性数值模型来模拟整个线路系统的渐进性坍塌，该模型将通过在WindEEE进行的试验进行实验验证。这项实验计划将利用大规模的风测试设备，将风测试带入故障调查的新境界。由于一条线路延伸数百公里，设计一条线路的所有铁塔以使其在极端HIW事件下不受损坏可能是非常昂贵和不切实际的。如本建议书所述，将制定基于性能的设计程序。所需的性能标准将包括最大限度地减少因部分线路故障而造成的电力中断的影响和持续时间，以及遏制这种故障。这项研究将为一个世界性问题找到可持续的解决方案，将为风荷载下结构的基于性能的设计建立一个框架，并将为6名研究生提供最先进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.