台风作用下大跨度桥梁非线性随机抖振响应等效静力风荷载研究

Southeast coastal area of China is one of the most typhoon prone areas in the world, and long-span bridges located here are significantly affected by typhoon winds. Existing researches show that typhoon winds exhibit different characteristics from monsoon winds and long-span bridges’ buffeting responses induced by typhoon winds are different from which induced by the monsoon winds. At present, the Chinese wind resistant design code for bridges is based on the monsoon winds and uses single-target equivalent static wind loading (ESWL) method to calculate long-span bridges’ buffeting responses. It is obvious that the current bridge wind resistant design code is unsuitable in typhoon prone areas. Another disadvantage of the current code is that only the buffeting response value on the equivalent point is equal to the real one. On the other points, values of buffeting response calculated by the code are different from the real extreme values more or less. This research project is proposed based on the above research status. According to the General Load-Response-Correlation method which has a flexible expression and proposed by the author, and the existing typhoon observation data, the typical typhoon wind characteristics of Chinese southeast coastal areas are summarized through probability statistics methods such as Monte-Carlo. After obtaining the basic typhoon wind parameters, long-span bridges’ ESWL of typhoon-induced buffeting response will be studied systematically by means of theoretical analysis, numerical calculation and wind tunnel tests. Finally, a multi-target ESWL calculation method which can consider the non-stationary, power spectrum density and turbulence intensity of the fluctuating wind, the geometrical nonlinear of the bridge, the instantaneous wind attack angle and other parameters, is proposed to deal with the typhoon-induced buffeting response of long-span bridges in southeast coastal areas of China. Meanwhile we hope the proposed method can provide theoretical support and reference for the revise of the long-span bridges’ wind resistant design code in the future.

我国东南沿海地区的大跨度桥梁受台风影响显著。研究表明，台风近地风特性及其作用下的大跨度桥梁抖振响应均不同于良态风气候。目前我国桥梁结构抗风规范仍以良态风为基础，采用单目标等效静力风荷载方法进行抖振响应的等代计算，不适用于台风环境，且仅能保证结构等效部位处的抖振响应极值相等。鉴于此，本项目以申请人提出的具有灵活分布形式的广义荷载-响应相关法和已有台风观测资料为基础，利用Monte-Carlo等概率统计方法总结归纳东南沿海地区典型台风近地风场特性，并采用理论分析、数值计算和风洞试验相结合的手段，综合考虑脉动风功率谱密度、紊流度和非平稳性、结构几何非线性、气动力瞬时风攻角等参数的影响，对大跨度桥梁抖振响应等效静力风荷载进行深入研究，以期建立适合我国东南沿海地区典型台风环境下的大跨度桥梁非线性随机抖振响应多目标等效静力风荷载计算方法，为今后我国桥梁结构抗风规范的修订提供理论方面的支持和参考。

目前，我国桥梁及建筑结构风荷载规范均采用年最大风速法确定东南沿海地区的基本设计风速，有可能低估台风的影响。同时，《公路桥梁抗风设计规范》采用静阵风等效静力风荷载进行抖振响应的等代计算，为典型的力等效原则计算方法。针对以上问题，本项目主要开展了两方面的研究：东南沿海地区台风气候模式下的基本设计风速确定；桥梁结构多目标等效静力风荷载计算方法。主要结果有：.（1）台风气候模式下基本风速确定。以福州地区为研究对象，根据《热带气旋年鉴》提供的1949-2015年的数据，采用Yan Meng台风工程模型对青州闽江大桥桥位处的风速进行了模拟，共获得153组风速样本。台风模拟中，最大风速半径和径向压力分布系数采用了赵林等以上海、浙江等地台风实测资料计算得到的经验公式。最后，采用极值I型概率分布对153组台风风速样本进行统计分析，获得桥位处100年重现期的台风气候模式下的设计风速为31.2m/s。此外，本项目进一步对青州闽江大桥在混合气候模式和台风气候模式下的抖振响应进行了比较。研究表明，基本设计风速是引起不同气候模式下抖振相应不同的主要原因。该研究在台风风速样本选取、台风工程模型正确性验证方面存在不足，目前应用于实际工程的充分性不足，有待做进一步的研究。.（2）桥梁结构多目标等效静力风荷载计算方法。本项目提出了以本征正交分解（POD）技术为基础的桥梁结构多目标等效静力风荷载基向量法。基向量法综合了LRC法、Universal法和PSWL法的各自特点。保留了LRC法能够反应脉动风荷载分布和结构响应分布主要信息的优点，改善了Universal法通过工程师个人判断选择等效静力风荷载基向量的不足，弥补了PSWL法没有考虑等效静力风荷载分布合理性和计算值不被高估的假设。东海大桥主航道桥算例表明，该方法在抖振响应计算精度和荷载分布的合理性方面均表现良好。同时，基向量法对申请人提出的GLRC法最佳荷载模式的选择提供了很好的借鉴，具有工程应用的前景。