大跨悬索桥吊索阻尼比影响因素分析

Analysis of factors influencing galloping on the straddle sling damping ratio of long-span suspension bridges

确定大跨悬索桥吊索的阻尼比及其影响因素是设计中的难点,且目前吊索流固耦合二维数值计算中吊索阻尼比取值的实际工程意义不太明确,为了利用二维流固耦合计算实际工程中吊索的风振特性,其中吊索断面刚度和阻尼的取值至关重要,为了研究吊索断面的阻尼特性,采用自由振动衰减法和有限元方法分析了吊索初始张力、长度、直径、风速、约束条件以及吊索位置对吊索阻尼比的影响。结果表明:吊索阻尼比随其初始张力的增大而增大,吊索阻尼比随其直径和长度的增大而减小;吊索阻尼比随风速的变化而变化;吊索两端为固定端约束时的阻尼比大于吊索两端为固定铰约束时的阻尼比;吊索的跨中阻尼比最小,从跨中向两端吊索阻尼比逐渐增大。因此在吊索流固耦合计算时,吊索阻尼比的取值随吊索初始张力、长度、直径、风速、约束条件以及吊索位置的不同而不同。

The definition of galloping on straddle sling damping ratio of long-span suspension bridges and its influencing factors analysis are the key problems encountered in the design, and at the moment, the sling damping ratio of practical engineering significance in sling two-dimensional fluid-structure interaction is uncertain. To take advantage of the two-dimensional fluid-structure coupling calculation of wind vibration characteristics of sling in practical engineering, in which, the stiffness and damping ration of the sling section is important. In order to study the damping characteristics of the sling section, free damped vibration and finite element method were used to analyze the influence of the sling damping ratio when sling initial tension, length, diameter, wind speed, constraints and sling position changes. The conclusions are drawn as follows： when the initial tension of sling is increasing, its damping ratio will increase; when the diameter and length of sling are increasing, its damping ratio will decrease. The damping ratio of sling is affected by wind speed. Comparing with the two ends of hinge constraint, the two ends of fixed constraint will be more beneficial to increase the damping ratio of sling. The damping ratio in the middle of sling is the smallest. From the middle to the end, the damping ratio of sling is gradually increasing. Therefore, calculating sling Fludi-Solid Coupling, the value of sling damping ratio differs depending on sling initial tension, length, diameter, wind speed, constraints and sling position.