Collaborative Research: Downburst Fragility Characterization of Transmission Line Systems Using Experimental and Validated Stochastic Numerical Simulations

下击暴流是指与雷暴相关的向下高强度风，对美国许多地区的输电网构成重大威胁。 考虑到输电基础设施的分布规模，将需要大量投资来升级现有系统，并适当设计新的基础设施以抵抗下击暴流风力。本研究的目标是开发一个综合的实验和数值框架，能够表征输电基础设施对抗下击暴流的脆弱性程度，并确定最关键的组件。该框架将提供有助于减少下击暴流引起的停电引起的社会混乱的知识，从而使国家在下击暴流事件后能够持续繁荣和福利。使用这个框架，传输系统的下击暴流性能和过去的故障的潜在原因的各种重要因素将被调查。此外，本研究将开发第一代下击暴流脆弱性模型的输电塔线系统（TLS）使用实验验证的数值模型。这些脆弱性模型对于输电网设计和管理的风险知情决策至关重要，以减轻未来的故障并增强电网对极端天气事件的弹性。数值和实验研究将提供所需的知识，以加强设计方法，包括下击暴流风荷载的输电线路系统。 研究结果将被整合到佛罗里达国际大学（FIU）和俄亥俄州州立大学的本科和研究生课程中，以更好地为未来一代基础设施工程师做好准备。项目数据将在NSF支持的自然灾害工程研究基础设施（NHERI）数据库（https：//www.DesignSafe-ci.org/）中存档并公开共享。这项研究将开发一个综合的实验和数值框架来表征输电线路系统对下击暴流的脆弱性。实验研究将涉及在佛罗里达大学的NSF支持的NHERI风墙（WOW）实验设施（EF）开发一个多功能的下击暴流模拟器。使用该模拟器，一个缩放，气动弹性多跨TLS将进行测试，其结果将用于实验验证耦合传输塔绝缘子导体基础系统的高保真有限元模型。通过这些实验和数值研究，将获得新的知识方面的空气动力学行为的导线和非天气下击暴流风场的网格塔节的阻力和屏蔽效应。此外，这些调查将揭示极端的非线性行为的输电线路系统在后弹性制度时，塔损坏或导体失败。该研究还将提供新的物理为基础的见解的作用，不确定性的下击暴流性能的TLS。与天气飓风载荷下的失效模式相比，非天气下击暴流载荷下的失效模式是唯一的或更可能发生的失效模式，将被识别和表征。所产生的数据和模型将被整合，以使用高效和准确的机器学习技术，在组件和系统层面开发下击暴流条件下TLS的第一代多维需求和脆弱性表面。此外，本发明还提供了一种方法，位于佛罗里达大学的NHERI WOW EF的实验性下击暴流模拟器将为自然灾害界提供一个独特的试验平台，该平台具有双重模拟能力，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查进行评估，被认为值得支持的搜索.

Downbursts, referring to downward high intensity winds associated with thunderstorms, pose a major threat to power transmission grids in many parts of the United States. Considering the distributed size of the power transmission infrastructure, significant investments will be needed in order to upgrade the existing systems and properly design new infrastructure to resist downburst wind forces. The goal of this research is to develop an integrative experimental and numerical framework that is capable of characterizing the extent of vulnerability of the power transmission infrastructure against downbursts, and identify the most critical components. The framework will provide knowledge that can help reduce outage-induced societal disruptions caused by downbursts, and thus enable continued national prosperity and welfare following a downburst event. Using this framework, various significant factors for the downburst performance of transmission systems and potential causes of past failures will be investigated. Moreover, this research will develop the first generation of downburst fragility models for transmission tower-line systems (TLSs) using experimentally validated numerical models. These fragility models are crucial for risk-informed decision making for design and management of the transmission grid in order to mitigate future failures and enhance the resiliency of the grid against extreme weather events. The numerical and experimental studies will provide the knowledge needed to enhance design methodologies to include downburst wind loads for transmission line systems. The research findings will be integrated into undergraduate and graduate courses at Florida International University (FIU) and The Ohio State University to better prepare the future generation of infrastructure engineers. Project data will be archived and publicly shared in the NSF-supported Natural Hazards Engineering Research Infrastructure (NHERI) Data Depot (https://www.DesignSafe-ci.org/). This research will develop an integrative experimental and numerical framework to characterize the fragility of transmission line systems against downbursts. The experimental research will involve developing a versatile downburst simulator at the NSF-supported NHERI Wall of Wind (WOW) Experimental Facility (EF) at FIU. Using this simulator, a scaled, aeroelastic multi-span TLS will be tested; the results will be used to experimentally validate high-fidelity finite element models of coupled transmission tower-insulator-conductor-foundation systems. Through these experimental and numerical investigations, new knowledge will be gained with regard to the aerodynamic behavior of conductors and drag and shielding effects on lattice tower sections under non-synoptic downburst wind fields. Moreover, these investigations will reveal extreme nonlinear behaviors of transmission line systems in post-elastic regimes when towers are damaged or conductors fail. The research also will provide new physics-based insights into the role of uncertainties in the downburst performance of TLSs. Failure modes that are unique to or are more likely to occur under non-synoptic downburst loadings, as compared to those under synoptic hurricane loadings, will be identified and characterized. The produced data and models will be integrated to develop the first generation of multi-dimensional demand and fragility surfaces for TLSs under downbursts at component- and system-levels using highly efficient and accurate machine learning techniques. In addition, the experimental downburst simulator at the NHERI WOW EF at FIU will provide the natural hazards community with a unique testbed with dual simulation capabilities to generate both non-synoptic and synoptic winds and analyze the impacts on buildings and other structural systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.