桥梁主梁CFD模拟之基准模型测压试验与气动特性分析

Pressure Measurement and Aerodynamics Investigation on Benchmark Model of Bridge Girder for CFD Simulations

为给桥梁CFD模拟提供基准数据，并研究裸梁和带栏杆梁的气动特性，开展了大带东桥加劲梁裸梁和成桥状态节段模型在不同风速和典型攻角（-6°～6°）下的风洞测压试验，获得了截面压力系数平均值和均方根（RMS）值分布及截面气动力系数。讨论了风工程用10英寸水柱量程压力扫描阀的压力系数RMS值的信噪比，分析了桥面栏杆对梁体表面压力系数平均值和RMS值分布、梁体气动力系数及漩涡脱落的影响。结果表明：典型攻角下大带东桥裸梁具有单一漩涡脱落St数，且其值明显大于成桥状态；成桥状态加劲梁因桥面栏杆的影响呈现复杂的漩涡脱落特征，展向不同截面漩涡脱落特性存在差异，但均呈现多峰值的多阶漩涡脱落特征，其峰值St数在0．08～0．15之间，也可见裸梁漩涡脱落St数；大跨度桥梁抗风设计需分别评价施工和成桥状态主梁脱落频率特性和结构涡振行为；应重视桥面栏杆对加劲梁气动力的影响，及其对桥梁主梁脱落行为的改变，并开展成桥状态桥梁的多阶涡振评价，在加劲梁外形设计中应综合考虑栏杆和梁体的气动行为。

In order to provide benchmark data of bridge girder for CFD simulations, and investigate aerodynamics of bridge girder with and without rails, wind tunnel tests on sectional model of main span of the Great Belt East Bridge in conditions of bare beam and completion status were carried out under various wind speeds and typical wind angles of attack ranged from -6° to 6°. The distributions of mean and RMS value of pressure coefficients on girder surface, as well as sectional aerodynamic coefficients were presented. The signal to noise ratio of the RMS value for commonly used pressure scanners with pressure span of 10 inches water column was discussed. Meanwhile the effects of deck rails on mean and RMS value of pressure coefficients on girder surface and aerodynamic coefficients, as well as on vortex shedding were also evaluated. The results show that under typical wind angle of attack, the bare deck presents only one vortex- shedding St number, which is significantly larger than that of girder in service. The stiffening girder in service presents complicated vortex-shedding features due to deck rails and there are slight differences among taped sections under common feature of multiple order vortex-shedding with peak values ranging from 0.08 to 0.15, and also with bare deck＇s St number included. It is concluded that for wind resistant design of large-span bridges, vortex shedding feature of girder and vortex-induced structural vibration should be investigated in both construction stage and service stage. Effects of the deck rails should be carefully investigated not only on girder aerodynamics, but also on girder vortex shedding pattern. The evaluation on multiple order vortex-induced vibration of bridges should also be carefully conducted, and aerodynamic behavior of deck rails and deck as a whole should be comprehensively considered in optimal design of the bridge girder.