外置纵向排水管对扁平钢箱梁涡振性能的影响及气动控制措施研究

Effects of external longitudinal drainage pipe on VIV performance of flat steel box girder and aerodynamic control measure

为研究外置纵向排水管对扁平箱梁涡振性能的影响,以某大跨度扁平钢箱梁悬索桥为工程背景,采用1∶50节段模型风洞试验,分别对有无外置纵向排水管的扁平箱梁涡振性能进行研究。试验结果表明:原设计扁平箱梁在0°与±3°风攻角下均发生显著涡激振动,通过在检修车轨道处设置内侧导流以及将外侧防撞栏杆隔二封一可以有效抑制断面涡振振幅至规范限值以下,但沿桥纵向设置外置排水管会显著降低主梁涡振性能,并使原有效涡振制振措施失效。通过计算流体动力学对主梁断面二维流场的模拟结果表明,外置纵向排水管会同时改变扁平箱梁断面下表面迎风侧与背风侧斜腹板处的旋涡脱落形态,在此基础上,通过在外置纵向排水管处增设导流板与水平稳定板用以改善该处的气体绕流形态,并据此提出了一种水平稳定板、导流板与间隔封闭栏杆共同作用的组合气动措施。试验结果表明,该组合措施能够显著抑制主梁的涡激振动,同时数值模拟结果表明,能够显著减弱斜腹板处的旋涡脱落现象,从而降低主梁受到的周期性涡激力,是该组合气动措施能够抑制梁体涡激振动的主要原因。

Here,to study effects of external longitudinal drainage pipe on vortex induced vibration(VIV)performance of flat box girder,taking a certain long-span flat steel box girder suspension bridge as the engineering background,1∶50 segment model wind tunnel tests were conducted to study VIV performance of flat box girder with and without external longitudinal drainage pipe.The test results showed that the originally designed flat box girder has significant VIV under wind attack angles of 0°and±3°,VIV amplitude of its section can be effectively restrained below the specification limit by setting inner diversion at track of maintenance vehicle and interval closed outer side anti-collision railings,however,setting external drainage pipe along bridge longitudinal direction can significantly reduce VIV performance of main beam,and make the original effective VIV control measures invalid.The computational fluid dynamic(CFD)simulation results of the two-dimensional flow field of main beam section showed that external longitudinal drainage pipe can simultaneously change vortex shedding forms at inclined webs on windward side and leeward side of lower surface of flat box girder section;then,gas flow around flat box girder section is improved by adding a deflector and a horizontal stabilizer at external longitudinal drainage pipe,accordingly a combined aerodynamic measure with joint action of horizontal stabilizer,deflector and interval closed railings is proposed.The test results also showed that the combined measure can significantly suppress VIV of main beam.Furthermore,the numerical simulation results showed that this measure can significantly reduce vortex shedding phenomenon at inclined webs to reduce main beam periodic vortex-induced force,which is the main reason why the combined aerodynamic measure can suppress VIV of girder body.