深切峡谷桥址区脉动风速相干函数风洞试验研究

The coherence function of fluctuating wind speed is a very important wind characteristic parameter in analyzing the buffeting response and flutter checking wind speed of the bridges. However, the value of the coherence function over a deep-cutting gorge is markedly different from that over the flat uniform terrain. To study the coherence function at the bridge site in a deep-cutting gorge, firstly, the coherence of fluctuating wind speed over an ideal gorge terrain is essentially analyzed by the wind tunnel test and the CFD numerical simulation methods. The optimization criterion of measuring points’ combination for analyzing the coherence of fluctuating wind speed over the gorge is developed, the influence mechanism of different factors on the coherence of fluctuating wind speed over the gorge is revealed, and then the basic form and parameters of the coherence function for the gorge terrain is summarized. Secondly, the coherence of fluctuating wind speed at the bridge site in an actual deep-cutting gorge terrain is investigated in a wind tunnel. According to the characteristics of the coherence of fluctuating wind speed at the bridge site in the deep-cutting gorge terrain, the ultimate form and parameters of the coherence function for the bridge site in the deep-cutting gorge terrain is proposed, and the applicability of Taylor's hypothesis in the deep-cutting gorge terrain is further discussed. Finally, the buffeting response and correction factor of flutter checking wind speed of the long-span bridge are analyzed based on the coherence function for the bridge site in the deep-cutting gorge terrain, and compared with the results analyzed by the routine analytical methods. This research could provide evidence for the wind-resistent design of the long-span bridges straddling the deep-cutting gorge and for improving the related contents in the current specifications.

脉动风速相干函数是分析大桥抖振响应及颤振检验风速时非常重要的风特性参数，但深切峡谷地形中脉动风速相干函数与常规平坦均匀场地的有明显不同。针对深切峡谷桥址区的脉动风速相干函数，首先，采用风洞试验并结合CFD数值模拟方法，对理想峡谷地形脉动风速相干性进行机理性分析，形成峡谷地形脉动风速相干性测点组合的优化准则，揭示不同因素对峡谷地形脉动风速相干性的影响机理，总结归纳出峡谷地形相干函数的基本形式与参数。其次，进行桥址区实际深切峡谷地形脉动风速相干性的风洞试验，根据桥址区深切峡谷地形脉动风速相干性的特点，提出深切峡谷桥址区相干函数的最终形式与参数，并讨论Taylor假设在深切峡谷地形中的适用程度。最后，根据深切峡谷桥址区的相干函数分析大跨度桥梁的抖振响应及颤振检验风速修正系数，并对比与常规分析方法的异同。本研究可为跨越深切峡谷的大跨度桥梁抗风设计提供科学支撑，也可为现有规范相关内容的完善提供依据。

脉动风速相干函数是大跨度桥梁风致响应分析中的重要参数，但深切峡谷地形中脉动风速相干函数与常规平坦均匀场地的有明显不同。针对深切峡谷桥址区的脉动风速相干函数及其对大跨度桥梁风致响应的影响，研究中推导并构造了理想峡谷地形与实际深切峡谷地形的边界过渡段模型；进行了理想峡谷地形风特性的风洞试验与数值模拟研究；开展了实际深切峡谷地形风特性的风洞试验；研究了复杂地形桥址区脉动风速相干函数的形式；在此基础上，考察了深切峡谷地形中非均匀风场对大跨度桥梁风致响应的影响。. 研究中针对理想峡谷地形与桥址区实际深切峡谷地形的风特性，首次提出了复杂地形模型边界过渡段的概念，并在理论上推导出一种曲线过渡段形式，且在实际复杂地形模型中提出采用三维渐变式过渡段。针对峡谷地形风特性的CFD数值模拟中来流边界条件无法准确给定的问题，提出了一种随高度变化的湍动能系数方法，并通过相应的风洞试验数据验证了该方法的准确性、有效性。提出将峡谷内的风特性沿高度方向分为受峡谷两侧山坡影响较为明显的峡谷内层部分以及受其影响不明显的峡谷外层部分。基于来流风谱及峡谷中心处与来流处脉动风速均方差的比值关系，提出了峡谷地形中心处风谱的推算公式，并验证了该推算公式适用于理想峡谷地形与桥址区实际深切峡谷地形。提出了一种具有普适性的脉动风速相干函数形式，并针对复杂地形桥址区给出了较合理的简化形式。揭示了山区峡谷地形下非均匀风攻角分布、非均匀风速分布、非均匀风速非均匀风攻角分布等非均匀风场条件对大跨度桥梁静风稳定性的影响。. 以上研究为更准确地开展峡谷地形风特性的风洞试验和数值模拟研究提供参考；同时，上述针对峡谷地形风特性的研究成果在一定程度上揭示了峡谷地形风特性的风场分布规律，可为处于山区峡谷复杂地形下的大跨度桥梁桥址区风特性研究及抗风设计提供指导。