大跨度桥梁超宽分体三箱梁抗风性能及控制措施研究

Study of Wind-Resistant Performance and Control Measures for Very Wide Girder with Three Separated Boxes in Long-Span Bridge

为研究超宽分体三箱梁的涡激振动特性及其抑振措施,以梁宽68 m的大跨斜拉-悬索协作体系公铁两用大桥为工程背景,采用缩尺比为1∶30的大比例节段模型进行风洞试验,研究主梁的涡振性能以及不同形式风屏障、桥梁附属设施对其影响和设置槽间开孔盖板的气动措施对其改善效果。研究结果表明:施工状态主梁断面没有出现明显涡振现象,主梁风屏障采用不规则开孔形式时的涡振性能优于等效栏杆形式;成桥状态主梁断面出现涡振现象,公路内侧栏杆对其涡振性能影响较大;通过施加30%透风率的错位圆孔槽间开孔盖板的气动优化措施可有效改善主梁涡振性能,优化后主梁无明显竖弯涡振现象,扭转位移振幅为0.07°,降低90%,同时断面具有优越的颤振性能,在此条件下随阻尼比的增加主梁涡振振幅明显降低,当扭转阻尼比增加至0.47%时主梁不出现涡振现象。

To study the characteristics of vortex-induced vibrations of very wide girder comprising three separated boxes and the vibration suppressing measures,a long-span combined cable-stayed and suspension bridge with deck width of 68 m is cited as a case.The segmental models at 1∶30 scale were prepared for wind tunnel tests,to study the vortex-induced vibrations of the main girder,the influence of various wind barriers and subsidiary facilities on the vortex-induced vibrations of the main girder,and the effect of adding perforated cover plates between the separated boxes on the improvement of the aerodynamic response of the main girder.The results demonstrate that no vortex-induced vibrations were observed on the main girder during construction,and the wind barriers with irregular perforations could mitigate the vortex-induced vibration of the main girder,the effect of which was better than that of equivalent balustrades.Whereas vortex-induced vibrations were monitored on the main girder in the completed bridge state,and the balustrades on the inner side of carriageways engaged significantly in these vibrations.By adding perforated cover plates with 30%void ratio in staggers,the vortex-induced vibrations on the main girder were effectively suppressed,and after optimization,no obvious flexural vibrations were monitored,with 0.07°of torsional movement,decreased by 90%.Meanwhile,the buffeting resistance of the man girder is good,with the increase of damping ratio,the amplitude of vortex-induced vibration of the main girder was significantly reduced,and when the damping ratio for torsional movement increased to 0.47%,no vortex-induced vibrations occurred on the main girder.