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

下暴，指的是与雷暴相关的向下的高强度风，对美国许多地区的输电网构成了重大威胁。考虑到电力传输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御下突风。本研究的目标是开发一个综合实验和数值框架，能够表征输电基础设施对下突的脆弱性程度，并确定最关键的组件。该框架将提供知识，帮助减少由崩溃引起的中断导致的社会混乱，从而在崩溃事件发生后实现持续的国家繁荣和福利。利用这一框架，将研究影响输电系统降突发性能的各种重要因素以及过去故障的潜在原因。此外，本研究将利用实验验证的数值模型开发输电塔线系统（TLSs）的第一代下突发脆弱性模型。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必要的知识，以提高设计方法，包括下击风负荷的输电线路系统。研究成果将被整合到佛罗里达国际大学（FIU）和俄亥俄州立大学的本科和研究生课程中，以更好地培养下一代基础设施工程师。项目数据将在nsf支持的自然灾害工程研究基础设施（NHERI）数据仓库（https://www.DesignSafe-ci.org/）中存档并公开共享。本研究将开发一个综合的实验和数值框架，以表征输电线路系统对降暴的脆弱性。实验研究将包括在FIU的nsf支持的NHERI风墙（WOW）实验设施（EF）上开发一个多功能的下击模拟器。利用该模拟器，将对一个按比例的气动弹性多跨TLS进行测试；结果将用于实验验证高保真耦合输电塔-绝缘子-导体-基础系统的有限元模型。通过这些实验和数值研究，将获得关于非天气降暴风场下导体的空气动力学行为以及晶格塔截面的阻力和屏蔽效应的新知识。此外，这些研究将揭示当塔损坏或导体失效时，输电线路系统在后弹性状态下的极端非线性行为。该研究还将为不确定性在tls下突性能中的作用提供新的基于物理的见解。与天气性飓风载荷相比，非天气性下暴雨载荷下特有的或更有可能发生的失效模式将被识别和表征。生成的数据和模型将被集成，使用高效和精确的机器学习技术，在组件和系统级别上为下爆下的tls开发第一代多维需求和脆弱性表面。此外，在FIU的NHERI WOW EF的实验下爆模拟器将为自然灾害社区提供一个独特的测试平台，具有双重模拟能力，可以产生非天气风和天气风，并分析对建筑物和其他结构系统的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.