山区峡谷处非平稳强风下大跨度桥梁风振响应和等效静风荷载研究

Wind load and wind-resistance bridge design are key problems for the construction of long-span bridges across deep valleys at mountain areas. Different from the winds in coastal areas and plains, the strong winds in mountain valleys have nonstationary and three-dimensional characteristics. Due to the complexity, the systematic research is relatively limited. Also corresponding wind parameters are not provided by current design specifications.. Based on existing wind data from field measurements at the bridge site in a mountain valley, and wind tunnel experiments and measurements of wind field and structural response to be conducted, this study will focus on wind spectrum estimation and modeling, wind field Monte Carlo simulation, bridge aerodynamic parameters measurement under time-varying mean wind speeds, and long-span bridge buffeting analysis and equivalent static loading under nonstationary winds. We will develop the new method to estimate the evolutionary spectrum, tentatively establish wind spectrum and coherence models and also explore terrain-dependent characteristics of winds in mountain valleys. Also, we will propose the efficient algorithms for the simulation, especially conditional simulation of nonstationary wind fields. Furthermore, we will explore the measurement to evaluate bridge aerodynamic parameters under time-varying mean wind speeds. Finally, we will develop the efficient algorithm of long-span bridge buffeting analysis and effective method to determine equivalent static loading under nonstationary winds. This research will not only significantly improve the understanding to wind characteristics in mountain valleys, but lay the foundation for the wind-resistance design of long-span bridges in mountain area as well.

风荷载和桥梁抗风设计是山区深切峡谷处大跨度桥梁建设的关键问题。与沿海平原等地区风场不同，山区峡谷风场具有非平稳性和三维性。鉴于其复杂性，相关系统研究较少，规范对相关的风参数也无明确规定。. 基于已有山区峡谷桥位处风速实测资料，并结合风洞试验和风速及结构响应实测，本项目将在脉动风功率谱评估及建模、发展风场快速模拟算法、时变平均风下桥梁气动参数测量和非平稳风下大跨度桥梁风振分析及等效静风荷载等方面展开研究。将发展非平稳过程演变功率谱评估方法，初步建立山区脉动风功率谱和相干函数模型，并探讨依赖于地形特征的山区峡谷风特性；同时提出风场模拟特别是非平稳风场条件模拟的快速算法；此外，探索时变平均风下桥梁三分力系数和气动导纳函数测量；最后发展非平稳风下大跨度桥梁风振分析高效算法及等效静风荷载确定方法。该项研究对理解山区深切峡谷风场特性有重要意义，是山区大跨度桥梁抗风设计的基础环节。

山区峡谷处风场复杂，非平稳性强，制约着大跨度桥梁的设计和运行。本项目以山区峡谷处大跨度桥梁为工程背景，基于前期已有山区峡谷桥位处风场实测数据，结合风洞试验以及风场实测，通过理论分析和数值模拟，探讨了非平稳风场时变相干函数的建模，研究了大跨桥梁非平稳风场的快速随机模拟，并发展了大跨桥梁非平稳响应分析方法，主要取得了如下成果：.1)揭示了Priestley演化谱理论在描述时变相干函数方面的缺陷，基于Wold-Cramer分解模型理论建立了非平稳脉动风时变相干函数模型，并进一步构建了考虑时变相干函数的非平稳风作用下结构动力响应频域分析框架。利用实测雷暴风数据，探讨了该模型的评估和在结构动力分析中的应用。.2)基于将沿直线分布的多点非平稳随机过程模拟转化为一维非平稳随机波模拟的思想，提出了一种基于随机波的多点非平稳随机过程模拟方法。并进一步通过采用本征正交分解对随机波的二维演化功率谱进行解耦，将非平稳非均质随机波的模拟转化为许多在时间和空间均匀调制的平稳均质随机波模拟之和，进而可采用二维FFT极大提高模拟效率。最后该方法被应用于包括大跨桥梁台风风场模拟在内的多个风场模拟中。.3)借助于本征正交分解，将FFT应用于具有时变相干函数的多点非平稳过程模拟中，并将该方法应用于多点雷暴风和大跨桥梁的台风风场模拟中。.4)提出了一种基于FFT的高效且准确方法来提高结构的非平稳随机响应分析的效率。分别提出了在均匀调制和一般调制的非平稳随机激励下，线性结构随机响应分析的FFT方法，将其拓展到非线性系统非平稳响应的等效线性化求解中，并应用于大跨桥梁的非平稳抖振响应分析中。.研究成果不仅能有效提高对山区非平稳强风的认识，丰富既有的风工程知识，而且还为山区峡谷处大跨度桥梁抗风设计奠定了理论基础。