基于分布式气动力的大跨度钢箱梁桥多尺度抖振应力响应时域分析及验证

With the span of bridges being becoming longer and longer, and the girder being becoming wider and more complex, the whole buffeting response of bridges cannot meet the needs of practical engineering. People still want to get the stress responses of local members to investigate the problems of fatigue and service performance. However, the finite element modeling technique and corresponding analytical method are not well developed for the purpose of the local buffeting stress analysis of long span bridges. Taking the theoretical analysis, wind tunnel experiments and field testing as the main means, this project will investigate the multiscale buffeting stress analysis of long-span bridges with steel box girders in the time domain based on distributed aerodynamic forces and verify its effectiveness. The main work includes the following aspects: .1) Build the framework of multiscale simulation of structures considering both the global and local responses..2) Present a distributed wind pressure model for steel box girders and develop a identification technique for the complex aerodynamic admittance functions of wind pressure..3) Present a distributed self-excited force model which is the function of displacement and velocity of points on sections of steel box girders, develop a test device of a spring suspension rigid body section model which can measure the multipoint pressure and vibrations synchronously, and present an identification technique for the aerodynamic parameters of the distributed self-excited force..4) Build the framework of the multiscale buffeting stress analysis of long-span bridges with steel box girders in the time domain considering both the global and local responses.

随着大跨度桥梁跨径越来越大、主梁断面宽度的不断增大和复杂化，桥梁的整体抖振响应已经不能满足实际工程的需要，人们还需要获得局部构件的应力响应来进行疲劳、服务性能等深入问题的研究。但目前以抖振的局部应力响应分析为目的的大跨度桥梁有限元建模技术以及相应分析方法还不成熟。本项目拟以理论分析、风洞试验和现场实测为主要手段，研究基于分布式气动力的大跨度钢箱梁桥的多尺度抖振应力响应时域分析方法并验证其有效性，主要包括：1）建立可以同时考虑整体和局部响应的结构多尺度模拟理论框架；2）提出一种针对钢箱梁断面的分布式抖振风压模型，建立复风压气动导纳函数识别技术；3）提出一种钢箱梁断面各点位移、速度函数的分布式自激力模型，开发一套同步多点测压测振的弹簧悬挂刚体节段模型测试装置，建立分布式自激力气动参数的识别技术；4）建立一种同时考虑整体和局部响应的大跨度钢箱梁桥多尺度抖振应力响应时域分析框架。

针对大跨度箱梁桥抖振疲劳评估的需要，本项目开展了大跨度桥梁多尺度建模技术和分布式气动力时域化方法研究，建立一种大跨度钢箱梁桥的抖振多尺度应力响应时域分析方法，为大跨度桥梁的安全运营和科学管理提供技术支持和保障。.主要研究成果如下：.（1）建立了连接不同尺度单元的高精度界面耦合方法，并验证了该方法的正确性；基于子结构法，建立了包含柔性中央扣局部索梁锚固系统的桥梁结构多尺度有限元模型，通过ANSYS APDL语言二次开发，实现了大桥三维非线性颤抖振时域分析。.（2）基于准定常理论，提出了一种分布式抖振力模型；研发了一种独立配置扭转刚度实现竖向扭转耦合大振幅自由振动的风洞实验系统。基于开发的大振幅测振装置，建立了基于幅变颤振导数的非线性自激力模型，进行大桥颤振非线性行为分析，研究发现了：由于桁架断面的复杂性使得其在各个攻角下都存在明显的软颤振行为即极限环振动，存在明显的非线性分叉现象，非风致气动阻尼非线性对其非线性软颤振行为贡献更大。.（3）为了验证本项目提出的多尺度建模方法以及分布式气动力模型的正确性，提出一种考虑纵向约束不确定性的桥梁有限元模型修正方法，开展了矮寨大桥关键构件应力现场监测研究，将现场监测的结果与数值计算结果进行对比，验证了本项目所提方法的正确性。