Π型钢-混叠合梁斜拉桥涡振性能及整流罩制振措施研究

Vortex-induced vibration performance of a cable-stayed bridge with a Π-shaped steel-concrete composite girder and aerodynamic countermeasure research

大跨度Π型钢-混叠合梁斜拉桥存在常遇风速下的涡激振动(vortex-induced vibration,VIV)。为了抑制涡激振动,采用1∶50节段模型风洞试验,研究了不同气动措施对主梁涡振制振的作用,包括下稳定板、导流板、裙板、整流罩等措施。试验结果表明,只有整流罩与下中央稳定板的组合气动措施能在不同风攻角和0.66%的阻尼条件下,将主梁的竖弯与扭转涡振振幅同时降低75%以上。在此基础上,通过提高整流罩竖板高度优化了该制振措施,继而开展的1∶20节段模型风洞试验的结果表明,优化后的措施能够完全消除Π型叠合梁在不同风攻角和0.5%小阻尼比下的涡激振动。最后,数值计算的结果表明,优化后的整流罩组合措施能够同时降低主梁上、下表面旋涡脱落尺寸,并显著减小主梁受到的周期性涡激力,从而达到抑制主梁涡振的效果。研究成果可为Π型钢-混叠合梁斜拉桥的涡振制振措施设计提供参考。

Vortex-induced vibration(VIV)of a long span cable-stayed bridge with a Π-shaped steel-concrete composite girder often occurs at frequent wind speeds.In order to suppress VIV of the girder,the effects of different measures on VIV were studied by using a 1∶50 scale section model wind tunnel test,including installing lower stabilizer,baffle,apron fairing and the combination of fairing and lower central stabilizer.Tests show that only the combination of the fairing and lower central stabilizer can reduce the vertical and torsional VIV amplitude of the girder by more than 75%under different wind attack angles and 0.66%damping conditions.On this basis,the height of the fairing vertical plate is increased,and the aerodynamic shape of the combination of the fairing and lower central stabilizer is further improved.The effectiveness of the measure was verified by a 1∶20 large-scale section model wind tunnel test.Finally,the VIV suppression mechanism of the aerodynamic measure was studied by using computational fluid dynamics.Results show that the combination of the fairing and lower central stabilizer can simultaneously reduce the vortex size on the upper and lower surfaces of the girder and effectively reduce the unsteady aerodynamic force on the girder,thereby suppressing the VIV of the girder.The research results can provide reference for the VIV performance design of theΠ-shaped steel-concrete composite girder of long span cable-stayed bridge.