流线型箱梁断面抖振力空间分布特性与三维气动导纳识别方法研究

Three-dimensional aerodynamic admittance and wind yaw angle are of great importance in determining the spatial distribution of gust loading on streamlined girders. However, the present identification approach of the three-dimensional aerodynamic admittance, based on simultaneous pressures measurements, cannot be applied to the bridge girders with complicated cross-section. Meanwhile, the study of the characteristics of buffeting forces under skew wind is far from sufficient. The two parameters have constrained the improvement of the buffering analysis of long-span bridges..This program is carried out based on the three-dimensional buffeting analysis theory for bluff bodies. Firstly, the spatial characteristics of buffeting forces on streamlined box girders under orthogonal wind are investigated by force measurements of sectional models with two sets of HFFBs (High Frequency Force Balance). The relationships of buffeting parameters between the ones obtained by force measurements and the ones by pressure measurements are revealed, and then the three-dimensional aerodynamic admittance of streamlined girders identified by forces measurements is proposed, which will be validated by free vibration tests of sectional model. Then, it is extended to box girders with complicated cross-section. Secondly, the two-dimensional aerodynamic admittance of the girders identified by force measurements on large aspect-ratio (span/width) sectional model with single HFFB is proposed. It can be applied to study the effect of three-dimensionality of turbulence on buffeting forces acting on streamlined box girders. Finally, the effects of skew winds on spatial distribution of buffeting forces are studied by wind tunnel experiments, which are used to propose a three-dimensional model of buffeting forces on streamlined box girders by taking the oncoming flow condition into consideration. These research results have an important significance to improve the present buffeting analysis approach.

三维气动导纳和风偏角是影响流线型箱梁断面抖振力空间分布特性的关键参数，目前的三维气动导纳测压识别方法对于复杂流线型箱梁断面存在明显的局限性，而斜风条件下抖振力特性的研究成果则更为匮乏，这些因素已成为大跨桥梁抖振精细化研究的一个瓶颈。.本课题以大跨度桥梁抖振分析理论为基础，首先利用节段模型双动态天平测力试验深入研究正交风作用下流线型箱梁断面的抖振力空间分布特性，揭示测力法和测压法所得抖振力参数之间的内在联系，建立三维气动导纳的测力识别法，并通过节段模型自由振动试验来验证，进而将该方法扩展至任意复杂桥梁断面；其次，发展箱梁断面二维气动导纳的大跨宽比节段模型单动态天平测力识别法，进而探明紊流三维效应对于流线型箱梁断面抖振力的影响程度；最后，通过研究斜风作用下流线型箱梁断面的抖振力空间分布特性，建立考虑来流条件的流线型箱梁断面三维实用抖振力模型。以上研究成果对完善现有的抖振分析方法有参考意义。

三维气动导纳和风的方向性是影响流线型箱梁断面抖振力空间分布特性的关键参数。为此，本课题针对复杂流线型箱梁断面，基于大跨桥梁三维抖振分析理论建立了测力法和测压法所得抖振力之间的内在数学联系，通过大量风洞试验验证了两种方法的一致性，提出基于测力法的三维气动导纳理论识别框架，发展了基于单天平测力法的二维气动导纳风洞试验方法，阐明了关键气动参数在复杂桥梁断面紊流三维效应中的作用机理。其次，本项目明确了风偏角对于脉动风速和抖振力空间相关性的影响，提出了斜风作用下抖振力相干函数模型和三维抖振力模型，发展了考虑风攻角影响的三维气动导纳闭合解理论分析框架，揭示风攻角对于抖振力特性的作用机理，为实现桥梁断面气动性能优化提供理论支撑。最后，本项目基于多风扇主动控制风洞发展了非平稳风场物理模拟方法，为大跨桥梁非平稳风荷载和风振响应研究提供新的试验途径和研究方法。本项目的研究成果对于提升我国大跨度桥梁抗风设计水平具有较高的理论价值和重大工程应用前景。