深切峡谷底斜拉桥颤振稳定性能研究

以峡谷底斜拉桥——迫龙沟大桥为工程背景,结合地形试验结果和大桥具体位置确定了桥位处的设计风参数;分别检验了小风攻角和大风攻角下颤振稳定性能,阐明了颤振临界风速随风攻角改变的变化规律;分析了颤振导数和系统阻尼的变化特征,获得了不同结构状态下主梁断面颤振驱动机理。结果表明:峡谷底桥梁的设计基准高度可参照跨中位置确定,颤振检验风速可按不同风攻角区间分别确定;颤振临界风速和颤振检验风速随风攻角的增大均呈降低趋势,但由于下降速率不同有可能出现小风攻角下颤振不失稳而大风攻角下颤振失稳的现象;不同风攻角状态下或施加气动措施前后,颤振导数和系统阻尼与折减风速的变化特征相似,表明颤振驱动机理和颤振形态均保持不变。

Experimental study on flutter performance of cable-stayed bridge at the bottom of a deep-cutting gorge

Polong Valley Bridge, located at the bottom of a deep-cutting gorge, was taken as the engineering background in this article. Firstly, the design wind parameters of the bridge site were determined based on the topographic experiment results and the bridge location. Then, the flutter stability performance of the bridge, under small and large wind attack angle, was investigated via the sectional model wind tunnel test. And the variation characteristics of the flutter critical wind speed with the attack angle changing, were also analyzed in this article. Finaly, the flutter-driving mechanism of different structure states, was studied based on the flutter derivatives and system torsional damping ratio. The results show that, the design standard height can be calculated in the reference of the elevation of mid-span, and the flutter checking wind speed should be determined in different wind attack angle regions respectively. Both the flutter critical wind speed and the flutter checking wind speed decreases with the wind attack angle increasing. However, because of different decreasing speed, there may be the phenomenon that it is stability under small wind attack angle but instability under large wind attack angle, when the bridge is under different wind attack angles or before and after setting aerodynamic mitigation measure, the flutter derivates and system damping ratio change similarly with the reduced widn speed increasing, which means that both the flutter-driving mechanisms and the flutter modality maintain the same characteristic.