刚构体系独塔斜拉桥施工期抖振响应

Buffeting Responses of Single-Tower Cable-Stayed Bridge with Rigid Frame System During Construction

为了更准确地计算桥梁抖振响应,以采用刚构体系的某带大挑臂钢箱结合梁独塔斜拉桥最大双悬臂施工阶段为研究对象,首先在有限元建模中重点讨论因塔梁固结处节点刚性区建模方法不同而导致的桥梁结构动力特性差异;随后运用二维不可压非定常雷诺平均URANS数值模拟方法,识别大挑臂钢箱主梁断面静力三分力系数和气动导纳;最后基于Davenport准定常理论在ANSYS中开展桥梁抖振时域分析,所得结果与气弹模型风洞试验进行比较.研究表明:施工阶段的独塔斜拉桥结构动力特性及抖振响应受塔梁结合处有限元建模方式影响十分显著,结构基频差异最大可达21.3%,进行此类桥梁动力分析时应予以足够重视;主梁断面的气动导纳识别结果表现出对来流风场参数的依赖性,抖振计算时应合理使用;主梁悬臂端抖振位移响应计算值大于风洞气弹模型试验测试值,该计算结果用于设计参考时是偏于保守的.

In order to estimate bridge buffeting responses more accurately,taking a large cantilever steel box composite girder of a single-tower cable-stayed bridge with rigid frame system under construction as the research object,a comparative study is made to investigate the differences in bridge dynamic characteristics caused by different modeling methods for tower-girder nodal rigid zone in finite element models.The two-dimensional incompressible unsteady Reynolds average Navier-Stocks(URANS)simulation method is used to identify aerodynamic admittances and static coefficients of the girder section,which consists of a steel box girder and large lateral cantilever arms.In addition,the quasi-steady buffeting theory of Davenport is carried out in ANSYS to analyze bridge responses in time domain,and the calculated buffeting responses are compared with those of the wind tunnel test of aeroelastic model.Results show that the structural dynamic characteristics and buffeting responses of the single-tower cable-stayed bridge with the maximum double cantilever in construction state are greatly affected by the finite element modeling method for the tower-girder binding zone.The maximum difference between structural fundamental frequencies reaches 21.3%,which deserves attention in similar dynamic analysis.The identified aerodynamic admittance of girder shows its dependence on parameters of incoming wind field,and should be utilized in a rational way.The calculated values of buffeting responses are found to be greater than that of the wind tunnel test of the aeroelastic model,and thus are conservative for structural design.