梁侧导流板对π型叠合梁断面涡振性能影响及抑振机理研究

Influence of guide plates on the side of the edge girder on the VIV performance of theπ-shaped composite deck section and its vibration suppression mechanism

具有开口形式的π型断面是一种易发生涡激振动(vortex-induced vibrations,VIVs)的钝体断面。为了准确把握某主跨520 m的π型叠合梁斜拉桥的涡振性能,开展了1∶25大尺度节段模型风洞试验,比较了在边主梁侧面布置不同的导流板(即梁侧导流板)对主梁涡振性能的影响。试验结果表明,原设计断面在-3°和-5°风攻角下存在显著的竖向涡振现象。当设置宽度为1.5 m、水平倾角为35°的梁侧导流板后,主梁在不同风攻角下均未发生涡振。通过对主梁绕流场数值模拟初步探讨了主梁发生竖向涡振的原因及导流板的抑振机理。模拟结果表明,导流板能够减小主梁底部区域旋涡的尺寸,使主梁上、下表面周期性压力差和气动力显著减小,从而削弱了诱发主梁涡振的条件,起到了抑制主梁竖向涡振的作用。该研究结果可为π型叠合梁断面的涡振抑振措施设计提供参考。

Theπ-shaped section with open form is a kind of bluff body section which is prone to the occurance of vortex-induced vibrations(VIVs).In order to elaborate the VIV performance of a cable-stayed bridge with theπ-shaped composite deck and the main span of 520 m,1∶25 large-scale section model wind tunnel tests were carried out to compare the effects of different guide plates arranged on the side of the edge girder on the VIV performance of the deck.The experimental results show that significant vertical VIVs exist at-3°and-5°wind attack angles in the original section design scheme.The guide plates on the side of the edge girder with the width of 1.5 m and 35°tilt angle can suppress VIVs at all of the wind attack angles.The causes of occuring vertical VIVs and the vibration suppression mechanism of the guide plates were analyzed preliminarily through the numerical simulation of the flow field around the deck.The results show that the guide plates help reduce the size of vortices under the deck,thus mitigate the aerodynamic force and the periodic pressure difference between the upper and lower surfaces of the deck.It is achieved that the factors inducing VIVs are controlled,and VIVs of the deck are suppressed.The results can provide a reference for the design of the aerodynamic countermeasures forπ-shaped composite deck sections.