大跨度斜拉桥桥塔自立状态抗风性能试验研究

Experimental Research on Wind Resistant Performance of Free-Standing Pylon of Long-Span Cable-Stayed Bridge

武汉青山长江公路大桥主桥为主跨938m的全飘浮体系斜拉桥,桥塔高度超过270 m。为了检验桥塔在施工阶段的抗风安全性,采用ANSYS软件分析该桥北塔结构动力特性,并制作缩尺比为1∶100的自立北塔气动弹性模型进行风洞试验,研究桥塔自立状态在均匀流场、紊流场中的涡振和驰振响应,以及在紊流场中的抖振响应。结果表明:桥塔自立状态在均匀流场中检验风速范围内仅发生了微小的涡振,未发生驰振现象;在紊流场中检验风速范围内桥塔未发生明显的涡振、驰振等现象;在紊流场中施工阶段设计基准风速作用下,桥塔顺桥向抖振位移远大于横桥向抖振位移,当风向角为15°及60°~75°时,桥塔塔顶顺桥向抖振位移均方根最大,为62~67 mm,不影响桥塔施工安全。

The main bridge of Qingshan Changjiang River Highway Bridge in Wuhan is a cable-stayed bridge with a main span of 938 m.The bridge is of a full-floating system,with pylons rising above 270 m.To verify the wind resistant performance of the pylons in the construction stage,the software ANSYS was used to analyze the dynamic property of the north pylon.And an aeroelastic model of the free-standing north pylon with a scale ratio of 1∶100 was built up to carry out wind tunnel test.Wind effects on the free-standing pylon were studied,including vortex-induced oscillation and galloping in both uniform flow field and turbulent flow field as well as the buffeting response in the turbulent flow field.The results show that only minor vortex-induced oscillation was observed on the free-standing pylon in the uniform flow field within the range of checking wind speeds,and no galloping occurred.In the turbulent flow field,no obvious vortex-induced oscillation and galloping has been detected on the pylon within the range of checking wind speeds.In the turbulent flow field,the buffeting-induced pylon displacement in the longitudinal direction was far bigger than that in the transverse direction,under the reference wind speed in the construction stage.When the wind yaw angle was at 15°and within the range of 60°to 75°,the root mean square of buffeting-induced pylon-top displacement in the longitudinal direction is the biggest,62-67 mm,which would not threaten the safety of bridge construction.