微椭圆截面斜拉索风致振动特性与机理

斜拉桥斜拉索在生产、运输、安装和运营过程中，在各种因素的作用下，有可能使得其截面形状不再是标准的圆截面，经过调研与统计，部分斜拉索具有长短轴之比接近1的微椭圆截面，研究微椭圆截面斜拉索气动力和风致振动特性具有重要工程价值。通过对3种长短轴之比（L/D=1.05，1.10及1.15）的微椭圆斜拉索模型进行测力和测振风洞试验，对比分析了微椭圆斜拉索与标准圆柱斜拉索的风致振动特性，研究了雷诺数、风攻角和长短轴之比对风致振动特性的影响规律，并尝试运用Den Hartog驰振准则对振动机理进行分析。研究结果表明：斜拉索的截面由标准圆变为微椭圆之后，在某些风攻角下振动更加剧烈，发生振动的雷诺数范围更宽，起振雷诺数更低；振动中心随雷诺数的变化曲线与标准圆柱斜拉索不同，并且随风攻角而异；大幅振动主要发生在临界区和超临界区，对应雷诺数为Re=2.5×10⁵~4.0×10⁵，风攻角则在α=10°~30°和α=60°~80°范围之内；风致振动特性随雷诺数的变化规律与长短轴之比不是简单的单调关系，而是与风攻角相关；根据Den Hartog驰振准则判断可能发生驰振的区域与试验中实际发生振动的区域吻合较好。

Wind-induced Vibration Characteristics and Mechanisms of Micro-elliptical Section Stay Cables

During their production, transportation, installation, and operation, stay cables of cable-stayed bridges may be affected by external factors such that their cross sections are no longer standard circular. Practical investigation has determined that the deformed cross sections of stay cables are micro-elliptical with a ratio of major-to-minor axes close to 1. Therefore, studying the aerodynamic force and vibration characteristics of micro-elliptical cross-section stay cables is of great engineering value. In this study, wind-induced vibration characteristics between micro-elliptical and standard cylindrical stay cables were compared and analyzed through wind tunnel tests on three micro-elliptical models with ratios of major-to-minor axes of 1.05, 1.10, and 1.15. The effects of the Reynolds number, wind angle of attack, and ratio of major-to-minor axes on the wind-induced vibration characteristics were studied. In addition, the Den Hartog galloping criterion was analyzed to reveal the mechanisms of vibration. The results show that when the sections of stay cables change from standard circular to micro-elliptical, the vibration becomes more intense at specific wind angles of attack. Moreover, the Reynolds number range of vibration increases and the lowest Reynolds number of vibration decreases. The curve of the vibration center versus the Reynolds number is different from that of the standard cylindrical stay cables, which considerably depends on the wind angle of attack. The large-scale vibration mainly occurs in the critical and supercritical regions corresponding to Reynolds numbers of 2.5×10⁵ and 4.0×10⁵ and wind angles of attack of 10°-30° and 60°-80°, respectively. The relationship between wind-induced vibration characteristics versus the Reynolds number and ratio of major-to-minor axes is not simply monotonous but is related to the wind angle of attack. The possible region of galloping calculated based on the Den Hartog galloping criterion is in good agreement with the region of actual vibration in the test.