桥梁复气动导纳函数的双格栅数控气流识别方法及其非线性特性研究

The design and construction of super-long-span bridges in China require more accurate buffeting response analysis, and aerodynamic admittance functions are the key factors to guarantee the accuracy in the analysis of buffeting response of bridges. However, due to the complexity of bridge aerodynamic admittance functions and practical limits of wind tunnel facilities, the identified aerodynamic admittance functions are scattered, hard to repeat and interpret. This remains an unsolved bottleneck problem in the long-span bridge wind-resistant design. This project plans to develop advanced computer-numerical-control (CNC) turbulence generation technique by invoking two separate active grids. Various wind flow including the quasi-sinusoidal turbulent flow, multi-frequency components harmonic turbulent flow and controllable wind spectrum turbulence can be generated in wind tunnel to study the identification method of complex aerodynamic admittance functions of bridge decks. The nonlinear property of bridge aerodynamic admittance functions and the dependence of the aerodynamic admittance functions on turbulence parameters will also be treated. The identified aerodynamic admittance functions along with the well-defined flutter derivatives will be explored to delineate intrinsic relations between them. The aeroelastic model of a simply-supported beam instrumented with force balance at its both ends will be developed to validate the identified complex aerodynamic admittance functions. The new method to identify the complex aerodynamic admittance functions of bridge decks accurately will be developed finally, which will play a part for accurate prediction of buffeting response of bridges during the development of super-long-span bridges in the future.

我国今后超大跨度桥梁的设计与施工要求更加准确的抖振响应分析，而气动导纳函数是抖振响应分析精度的控制性参数。由于桥梁气动导纳函数本身的复杂性和试验技术条件的限制，现有气动导纳的识别方法存在离散性大、重复精度低的缺点，这已成为我国超大跨度桥梁抗风设计中的一个技术瓶颈问题。本项目拟开发先进的分离双格栅数控气流试验技术，在风洞内生成准正弦脉动风场、多频合成谐波脉动风场和可控风谱的随机紊流风场，研究桥梁断面的复气动导纳函数识别方法，考察气动导纳函数的非线性特性及其与紊流参数之间的相互关系。综合运用上述气动导纳识别方法和已开发的气动导数强迫振动识别技术，研究气动导纳函数与气动导数之间的相互转化关系。通过安装测力天平的气动弹性简支梁模型对识别的复气动导纳函数进行验证，最终建立能准确识别桥梁结构复气动导纳函数的新方法，以为今后超大跨度桥梁建设进行准确的抖振响应分析奠定基础。

气动导纳函数是大跨度桥梁抖振响应分析中的关键参数，但目前桥梁气动导纳函数识别存在离散性大、重复精度低的问题，至今仍然是桥梁结构抗风领域的难点问题之一。本项目以开发新的气动导纳函数识别技术为目标，首先研发了一套数控双主动格栅装置，可以有效地在风洞中生成频率可控的准正弦脉动风场、多频率合成谐波脉动风场与随机脉动风场；然后依之为基础研究了桥梁复气动导纳函数的识别方法，基于现有的单频率识别方法、互功率谱法、自谱交叉谱综合最小二乘识别方法进行了比较研究，发现单频率识别方法的曲线光滑、重复性好；进一步分析研究了抖振力的非线性特性，并基于主动格栅识别技术和强迫振动技术比较研究了气动导纳和气动导数之间的转化关系；最后，通过两端安装测力天平的气动弹性简支梁模型风洞试验对不同风场识别的气动导纳和抖振力相关性等进行了对比验证，证实了主动格栅识别技术得到的气动导纳函数具有更高的重复精度。本项目开发的双主动格栅数控气流识别技术为研究与实际应用桥梁气动导纳函数提供了新的手段，为提高大跨度桥梁抖振响应的分析精度奠定了坚实的基础。本项目研究发表论文8篇，其中SCI论文4篇，EI/CSCD中文期刊论文4篇，获得发明专利授权2项，获得科技奖励2项，培养博士与硕士研究生共12名。