大跨度三主桁钢桁拱桥施工状态抖振风洞试验研究

Wind Tunnel Test on Buffeting of Long-Span Three-Truss Steel Arch Bridge under Construction

为研究大跨度拱桥施工状态的风致抖振性能,以三主桁钢桁拱桥——明珠湾大桥为背景,采用风洞试验对紊流风作用下的桥梁抖振响应进行测试。根据施工步骤选取典型施工状态,建立桥梁结构有限元模型并进行动力特性分析,通过比较自振模态频率,确定最不利施工状态。制作最不利施工状态下桥梁1∶100缩尺气弹模型,采用U形弹簧等效模拟梁、拱刚度,在模拟B类风场的边界层风洞中进行桥梁气弹模型抖振响应测试。结果表明:梁、拱已拼装至最大单悬臂且第3层扣索尚未张拉时为最不利施工状态;抖振随机响应以一阶竖弯和一阶横弯为主,抖振响应峰值因子与规范取值范围基本吻合;完全横桥向来风条件下拱桥抖振响应最大,完全顺桥向来风时抖振响应最小。

The Mingzhu Bay Bridge,a three-truss steel arch bridge,is used as the engineering background to examine the wind-induced buffeting performance of the long-span arch bridge in construction stage.Wind tunnel tests were conducted to evaluate the buffeting response of the bridge under turbulent winds.Typical construction states were extracted in accordance with the construction steps,based on which finite element model was established for dynamic property analysis.The natural modal frequencies were compared to pick up the most unfavorable construction state.An aeroelastic model of 1∶100 scale was built for wind tunnel test when the bridge was in the most unfavorable construction state.The equivalent stiffness of the girder and arch was simulated by the U-shaped springs.The buffeting response of the aeroelastic model was tested in the boundary layer wind tunnel under B wind exposure.According to the study,when the girder and the arch were assembled to be the longest cantilevers and the fastening stays of the third layer have not been stressed yet,the structure is considered in the most unfavorable construction state.The first-mode vertical bending and first-mode transverse bending are the dominant stochastic buffeting.The peak factor of the buffeting response is basically within the range given in the code.The maximum buffeting response occurs under crosswinds,while the minimum buffeting response appears under winds along the girder axis.