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

下击暴流和龙卷风属于被称为高强度风（HIW）的一类风暴。建议的研究重点是这些极端事件对传输线（TL）结构的影响。在加拿大和其他国家，每年都有高强度爆炸事件期间这些结构的破坏事件发生，造成了巨大的经济损失。在风对结构的影响方面，西方一直处于领先地位。它的研究能力得到了加强，建立了一个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场由平均值和湍流分量组成，这两者都取决于场地地形是开放的、郊区的还是城市的。在其上一个DG中，申请人侧重于在开阔地形的情况下HIW场的平均分量对TL的影响。 随着来自Windcraft的HIW现场数据的可用性，研究将被带到更高的水平。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峰值力的关键位置。分析将考虑湍流产生的动态效应。结果将采用荷载工况的形式，模拟HIW平均分量在各种地形条件下的临界效应，以及放大这些荷载以考虑动态效应的阵风响应系数。当输电塔倒塌时，所连接的导体的脱离导致作用在后续塔上的不平衡纵向力的产生，从而引起一连串的塔故障。将开发一种新的非线性数值模型来模拟整个线路系统的连续倒塌，并将通过在Windmill进行的测试进行实验验证。该实验计划将风测试到新的视野，故障调查，受益于一个大规模的风测试设施的可用性。由于TL延伸数百公里，因此将线路的所有塔设计成在极端HIW事件下保持不损坏可能是非常昂贵且不切实际的。将按照本建议书所述，制定基于性能的设计程序。所需的性能标准将涉及最大限度地减少由于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。该研究将为一个全球性问题找到一个可持续的解决方案，将为风荷载下的结构性能设计建立一个框架，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.