非平稳风作用下大跨度桥梁抖振响应时频混合分析方法研究

A typhoon happening in the southeast of China taken as the research object, the measured data are proceeded by the refined HHT method firstly. And then the buffeting force time-varying model and the self-excited force time-varying model are both proposed based on the time-varying mean wind speed, time-varying wind yaw angle and time-varying wind attack angle. After that, the buffeting governing equation is solved by the combination of the pseudo-excitation method and precise integration method. Finally, the buffeting response time-frequency domain analysis of long-span bridge under the unstationary wind is established and its calculation program is also developed. In addition, a long-span bridge near the area where the typhoon took place taken as the caculation example, the aerodynamic derivatives, the aerodynamic admittances, the three-component coefficents and its derivatives are identified respectively by the spring suspension sectional model test and motionless sectionla model test firstly. Then the buffeting response under the sationary wind and that under the unstationary wind are calculated respectively. Finally, to anlyze the calculation results and verify the method mentioned above, the calculation result of the buffeting response under the unstationary wind is compared with that under the staitonary wind and the full bridge aeroelastic model wind tunnel test respectively. The sea bay and estuary crossing projects in southeast China include many super larger bridge constructions, which put forward the requirment of the wind-resistantand design under the unstationary wind because southeast China is the area where typoons hit frequently. However, the conventional buffeting response analysis theories and calculation methods are not applicable for the buffeting analysis of bridges under the unstationary wind, and the buffeting response analysis theory under the unstationary wind is researched rarely up to now. Therefore, the research of this item is of greatly practical significance to the wind-resistant safety of long-span bridges and is also of greatly theoretical significance to the development of wind-resistant design theories on long-span bridges.

以我国东南沿海地区某台风为研究对象，采用改进HHT方法处理台风实测数据，建立变平均风速、变风偏角和变风攻角的抖振力时变模型和自激力时变模型，结合虚拟激励法和精细积分法求解结构振动控制方程，建立非平稳风下大跨度桥梁抖振时频混合分析方法，并开发计算程序。然后选取台风区域大跨度桥梁为算例，采用节段模型测振和测力方法分别识别变平均风和变风攻角下主梁断面气动导数、气动导纳、三分力系数及其导数，计算非平稳风下该桥梁抖振响应，并将结果与平稳风下计算结果和试验结果分别进行对比和验证。东南海湾、河口的跨越工程将涉及许多超大跨度桥梁的建设，该区域正是我国台风等非平稳风最活跃地区，建立在平稳风下的现有抖振响应分析理论和计算方法已不能满足需求。然而，至今非平稳风下大跨度桥梁随机抖振的理论分析研究还很少，因此本项目研究对确保大跨度桥梁的抗风安全性具有重大的实际意义，对大跨度桥梁抗风设计理论的发展也具重大的。

以台风“黑格比”实测数据为非平稳风研究对象，采用多重经验模态分解（EMD）法进行台风脉动风速平稳化处理，进而获得平稳化后的台风演变谱和慢变调制函数。台风脉动风速平稳化处理结果表明：平稳段的随机脉动风速一般只需经过一次EMD分解即可获得平稳化的随机脉动风速和慢变调制函数，而突变段的随机脉动风速一般要经过多重EMD分解方可获得平稳化的随机脉动风速和慢变调制函数。此外，EMD分解时矩大小对平稳化处理有一定的影响，可以通过多次尝试的方法获得较为理想的时矩大小。基于传统抖振分析假定和斜风抖振理论，建立了考虑时变平均风速、时变风偏角和时变风攻角的时变抖振力模型和时变自激力模型，在有限元框架下建立了大跨度桥梁随机抖振响应分析的时变控制方程，并利用虚拟激励快速算法获得了非平稳随机抖振响应。基于非平稳风作用下的大跨度桥梁随机抖振时频混合分析方法、Fortan 95和Matlab软件平台，开发了一套具有平稳风和非平稳作用下大跨度桥梁随机抖振响应分析的计算软件。以南京长江三桥为工程背景，以台风“黑格比”实测数据为非平稳风荷载，进行了南京长江三桥最大单悬臂状态下的随机抖振响应分析，并将计算结果与平稳风理论下的随机抖振响应进行对比。此外，还分析了时变气动力系数和时变自激力对非平稳随机抖振响应的影响。结果表明：非平稳随机抖振响应根方差最大值要明显大于平稳随机抖振响应，时变气动力系数对非平稳随机抖振响应影响较为明显，而时变自激力对非平稳随机抖振响应影响较小，甚至可以忽略不计。东南海湾、河口的跨越工程将涉及许多超大跨度桥梁的建设，该区域正是我国台风等非平稳风最活跃地区，建立在平稳风下的现有抖振响应分析理论和计算方法已不能满足需求。因此本课题的研究对确保大跨度桥梁的抗风安全性具有重大的实际意义，对大跨度桥梁抗风设计理论的发展也具重大的理论意义，研究结果可供工程界借鉴。