紊流积分尺度对桥梁抖振响应作用效应分析

Effects of turbulence integral scale on buffeting responses of bridges

紊流积分尺度的大小决定了脉动风对结构的影响范围,在结构风振响应分析中具有不可忽略的意义。通常在被动发生紊流风洞试验中,来流积分尺度难于有效模拟,紊流积分尺度对于结构风振响应作用效应缺少合理评价。针对我国已建成的几座大跨度桥梁,利用桥梁二维抖振频域分析方法,结合主梁节段模型风洞试验气动力参数识别结果,对不同紊流积分尺度下的桥梁抖振响应进行对比分析,研究了不同紊流积分尺度脉动风作用下,桥梁结构基频对应风谱能量和抖振响应的差别。分析表明,通常情况下,小比例模型(缩尺比1:400-1:600)紊流积分尺度能够较好的满足相似比要求,往往使得风洞试验的抖振计算结果更接近真实值。大比例模型(缩尺比1:20-1:40)的紊流积分尺度相似性严重偏离,需要对风洞试验结果进行修正。

The turbulence integral scale determines the influenced range of fluctuating wind on the structures,therefore has significant meaning in wind-induced vibration response analysis.Usually,in the passive turbulence wind tunnel,the integral scale of the flow is hard to be effectively simulated,so the effects on the buffeting responses of bridges influenced by different turbulence integral scale lack reasonable assessment.For several domestic built long-span bridges,using two-dimensional bridge buffeting frequency domain analysis method,combining with the aerodynamic parameters identified from wind tunnel tests,the comparison of buffeting responses considering different turbulence integral scales was carried out.The difference between the fundamental frequencies of the wind spectrum and buffeting response spectrum was compared under turbulent winds with different integral scales.The analysis shows that normally the small-scale model tests (scaling factor 1:400-1:600) can meet well the integral scale similarity requirement,thus the wind tunnel test results are closer to the true values.The large-scale model tests (scaling factor 1:20-1:40) are seriously deviated from the integral scale similarity requirement,thus the test results need to be revised.