Parameter identification of wind-induced buffeting loads and onset criteria for dry-cable galloping of yawed/inclined cables
Parameter identification of wind-induced buffeting loads and onset criteria for dry-cable galloping of yawed/inclined cables
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DOI：
10.1016/j.engstruct.2018.11.049
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发表时间：
2019-02
影响因子：
5.5
通讯作者：
M. Jafari;P. Sarkar
中科院分区：
文献类型：
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作者：
M. Jafari;P. Sarkar
悬索桥、斜拉桥、系杆拱桥、悬挑屋盖和输电线路的拉索，由于固有阻尼较小，容易在风中产生中到大的振动。由于这些振动引起的拉索的结构或疲劳失效，对这些结构的安全性和可用性构成了严重的威胁。在过去的几十年里，许多研究对引起不同类型的流致拉索振动的机理进行了研究，如风雨激振(RWIV)、涡激振动(VIV)、结冰的拉索舞动、尾流舞动和干索舞动，这些研究使人们对这些振动的原因有了更好的理解。在这项研究中，确定了控制倾斜和偏航干索的湍流诱导(抖振)和运动诱导风荷载(自激)的参数。这些参数有助于预测它们在湍流风中的响应，并估计干缆舞动的起始条件。通过风洞实验测量了偏航干索的气动力和气弹力参数。这项研究主要是通过测量气动阻尼和刚度来预测临界折减速度(R Vcr)作为当量偏航角(β*)和Scrton数(Sc)的函数。在位于爱荷华州立大学的AABL风与风隧道中，利用光滑电缆截面模型进行了均匀和光滑/阵风流动条件下的风洞试验。等效横摆角为0~45°的静力模型试验表明，偏航索的平均阻力系数(CD)和斯特劳哈尔数(S T)随偏航角的增大而减小，而平均升力系数(C L)在亚临界雷诺数(Re)范围内保持为零。通过横风向和顺风向单自由度动态模型试验，识别出了某一等效偏航角范围内的抖振特征导数函数和颤振导数。提出了偏航缆索平均阻力系数、斯特劳哈尔数、抖振指数导数函数和干索驰振临界折合速度的经验公式。结果表明，干索驰振的临界等效偏航角为45°。介绍了一种简化的设计方法，以估算防止干索舞动发生在设计风速以下所需的最小阻尼值。此外，本研究的结果还可用于预测某一特定风速、某一偏航角下的干缆的风荷载和响应。
Cables of suspension, cable-stayed and tied-arch bridges, suspended roofs, and power transmission lines are prone to moderate to large-amplitude vibrations in wind because of their low inherent damping. Structural or fatigue failure of a cable, due to these vibrations, pose a significant threat to the safety and serviceability of these structures. Over the past few decades, many studies have investigated the mechanisms that cause different types of flow-induced vibrations in cables such as rain-wind induced vibration (RWIV), vortex-induced vibration (VIV), iced cable galloping, wake galloping, and dry-cable galloping that have resulted in an improved understanding of the cause of these vibrations. In this study, the parameters governing the turbulence-induced (buffeting) and motion-induced wind loads (self-excited) for inclined and yawed dry cables have been identified. These parameters facilitate the prediction of their response in turbulent wind and estimate the incipient condition for onset of dry-cable galloping. Wind tunnel experiments were performed to measure the parameters governing the aerodynamic and aeroelastic forces on a yawed dry cable. This study mainly focuses on the prediction of critical reduced velocity (R V cr) as a function of equivalent yaw angle (β*) and Scruton number (Sc) through measurement of aerodynamic-damping and stiffness. Wind tunnel tests using a section model of a smooth cable were performed under uniform and smooth/gusty flow conditions in the AABL Wind and Gust Tunnel located at Iowa State University. Static model tests for equivalent yaw angles of 0–45° indicate that the mean drag coefficient (C D) and Strouhal number (S t) of a yawed cable decreases with the yaw angle, while the mean lift coefficient (C L) remains zero in the subcritical Reynolds number (Re) regime. Dynamic one degree-of-freedom model tests in across-wind and along-wind directions resulted in the identification of buffeting indicial derivative functions and flutter derivatives of a yawed cable for a range of equivalent yaw angles. Empirical equations for mean drag coefficient, Strouhal number, buffeting indicial derivative functions and critical reduced velocity for dry-cable galloping are proposed for yawed cables. The results indicate a critical equivalent yaw angle of 45° for dry-cable galloping. A simplified design procedure is introduced to estimate the minimum damping required to arrest dry-cable galloping from occurring below the design wind speed of the cable structure. Furthermore, the results from this study can be applied to predict the wind load and response of a dry cable at a specified wind speed for a given yaw angle.