EAPSI: Improving the Safety and Durability of Cable-supported Bridges in Wind

大跨度缆索支撑的行人桥由于其轻便和灵活的特性，特别容易受到风的影响。该项目旨在确定标准悬索桥的关键特征，以预测结构在风事件中的反应。这项研究将与著名风力工程专家葛耀军博士合作进行。上海同济大学最先进的风洞设施将提供进行全尺寸甲板截面风洞实验的独特机会，该实验将用于评估这种类型的桥梁在风暴情况下的安全性，并为跨度限制和风缓解策略提供指导。这些人行桥的动力特性还不为人所知，也没有对风荷载作用下的结构进行过试验研究。发现它们的基本特性将为研究柔性桥梁结构的非线性特性奠定基础。开发一个预测风分析框架，并最终制定一个设计标准，将柔性人行桥的风脆弱性纳入其中，这取决于对桥面空气动力学特性的识别。该框架将包含一个在ANSYS中建立的数值模型，该模型使用依赖于截面模型风洞试验的颤振和抖振力。桥面运动将在垂直和旋转方向上以两个自由度建模。这些风致荷载将使用传统和更新的方案进行建模。这些方案需要在风洞中使用截面模型测试来测量空气动力学系数以及空气动力学和空气弹性传递函数。获取来自许多现有行人桥的全尺寸监测数据（包含该标准甲板细节）将允许前所未有地了解如何在混合风洞/计算方法中对这些类型的桥梁进行建模，以及捕获可能扭曲响应预测比较的任何缩放误差的前景与实际结构在风荷载作用下的观测行为相比较。该奖项由美国国家科学基金会EAPSI与中国科技部合作资助，支持一名美国研究生的研究。

Long span cable-supported footbridges are particularly vulnerable to wind-induced failure due to their light and flexible nature. This project seeks to identify key characteristics of a standardized suspension footbridge in order to predict how the structure will respond during a wind event. This research will be conducted in collaboration with Dr. Ge Yaojun, a noted wind engineering expert. State of the art wind tunnel facilities at Tongji University in Shanghai will afford the unique opportunity to perform full-scale deck section wind tunnel experiments which will be used to assess safety of this type of bridge in the event of a wind storm and provide guidelines for span limits and wind mitigation strategies. The dynamic characteristics of these footbridges are widely unknown and no previous experimental investigation of the structures under wind loading has been performed. Discovering their fundamental characteristics will lay the groundwork for the structures to serve as a test bed for the investigation of non-linear features in the behavior of flexible bridge structures.Developing a predictive wind analysis framework and ultimately a design standard which incorporates wind vulnerability for flexible footbridges hinges on the identification of bridge deck aerodynamic characteristics. The framework will incorporate a numerical model built in ANSYS which uses flutter and buffeting forces reliant on section model wind tunnel tests. Bridge deck motion will be modeled with two degrees of freedom in the vertical and rotational directions. These wind-induced loads will be modeled using both traditional and updated schemes. These schemes require aerodynamic coefficients and aerodynamic and aeroelastic transfer functions measured using section model tests in the wind tunnel Access to full scale monitoring data from a number of existing footbridges which incorporate this standard deck detail will allow for an unprecedented look at how one can model these types of bridges in a hybrid wind tunnel/computational approach and also the prospect of capturing any scaling error that may distort response predictions compared to the observed behavior of the actual structure under wind loads. This NSF EAPSI award support the research of a U.S. graduate student and is funded in collaboration with the Chinese Ministry of Science and Technology.