开口断面桥梁颤振稳定性及优化措施机理研究

基于数值计算方法研究了开口断面主梁的颤振稳定性及下稳定板的作用机理.通过对比风洞试验的三分力及颤振临界风速结果,验证数值计算方法的可靠性,借助流场可视化直观地分析了颤振机理及下稳定板的抑制机理.结果 表明:来流在上游栏杆、上游箱室底板及下检修道处分离形成旋涡并向下游发展,期间产生与桥断面运动方向相同的气动力,成为颤振发散主导因素.在桥梁断面增设下稳定板能形成稳定的旋涡,气动力总体做负功,有效地抑制了颤振发散.增设1/4下稳定板,稳定板间形成了稳定的旋涡,气动力在运动周期内持续做负功,而同时增设下中央稳定板和1/4下稳定板在上游检修道与稳定板间形成的旋涡与上表面的旋涡交替主导气动力的方向,气动力先做负功后做正功再做负功.故只增设1/4下稳定板相比同时增设1/4下稳定板和下中央稳定板更有利于改善主梁的颤振稳定性能.研究结果能给同类型桥梁断面颤振抑振措施的选取提供参考.

Study on Flutter Stability and Mechanism of Optimization Measure for Open-cross-section Girder

The mechanism of flutter stability of open-cross-section and lower stabilizers are studied by numeri? cal calculation. The reliability of the numerical method is verified by comparing the wind tunnel test results of aerody? namic force coefficients and critical flutter wind speed. The mechanism of flutter instability and the suppression mechanism of lower stabilizers are analyzed intuitively by visual flow field. The results show that the incoming flow is separated from the upstream railing, the upstream of box room bottom and the lower inspection access road. Vortices are formed upstream and developed downstream of the girder. During this period, the aerodynamic force with the same motion direction as the girder is generated, which becomes the dominant factor of flutter divergence. The lower stabilizers are added to the girder to form stable vortices on the lower surface, which effectively suppresses the flutter divergence. By adding 1/4 lower stabilizers, stable vortices are formed between the stabilizers, and the aerodynamic force continues to do negative work in the motion cycle. However, by adding the lower central stabilizer and 1/4 lower stabilizers at the same time, the vortices formed between the upper inspection access road and the stabilizers alter? nately dominate the direction of aerodynamic force with the vortex on the upper surface. Aerodynamic forces do nega? tive work first, then positive work and eventually negative work in the motion cycle. Flutter stability of the girder is more beneficial to be improved by adding only 1/4 lower stabilizers than adding both 1/4 lower stabilizers and lower central stabilizers. The research results can provide a reference for the selection of flutter suppression measures of the same type of girder.