基于风振制振原理的大跨度桥梁箱形主梁气动外形优化

China is one of the few countries in the world, which are severely affected by wind hazards and disasters. Extreme wind loads caused by strong wind often become the key factor in bridge designing and construction. In order to improve aerodynamic performance, it usually takes a lot of effort and time to find effective control measures for wind-induced vibrations. However, the fundamental reason for this is the fact that the original bridge component has certain defects in the aspect of aerodynamic performance. If the aerodynamic configuration optimization of bridge components can be realized based on the clarification of mechanism for various wind-induced vibrations, especially the flow patterns around structures that intrinsically linked to structural aerodynamic performance, the level and efficiency of wind-resistant study can be effectively improved. Based on this idea, aerodynamic configuration optimization method for bridge components in the aspect of aerodynamic performance, which has a combination of both macro and micro levels, will be established in this project, through theoretical analysis on the inherent mechanism of wind-induced vibrations for bridges, with the help of quantitative flow field visualization technique featured in Particle Image Velocimetry and supplemented by numerical simulation. With this method, the aerodynamic configuration of closed box girder and twin box girder, which may become the potential candidates to be applied to super long-span bridges, will and can be initiatively optimized based on aerodynamic performance. And the parametric analysis and ratings for the structural wind-resistant performance induced by different sets of critical shape parameters will also be conducted to meet with the service requirements of different levels. The expected research results in this project will be a substantial improvement and breakthrough to wind-resistant fundamental theories for bridges, and provide a solid technical support to the constructions of long-span bridges.

我国是世界上少数几个受风灾影响最严重的国家之一，强风引起的极值风荷载往往成为控制桥梁设计和施工的关键因素。为了改善气动性能，桥梁抗风研究中往往需要花费大量人力物力和时间来寻找有效的风振控制措施，而其根本原因是原始桥梁构件在空气动力性能方面的某种“缺陷”。如能在掌握风振机理、特别是结构绕流流态特征同风振性能内在联系的基础上实现桥梁构件的气动外形优化，就能有效提升抗风研究的水平和效率。基于这一研究思路，项目采用以粒子图像测速技术为主、数值模拟为辅的流场定量可视化技术，从桥梁风振现象的内在机理分析理论出发，建立宏观和细观层面相结合的桥梁构件抗风性能优化方法，实现主动地对可能应用于超大跨度桥梁的扁平闭口箱梁和分体箱梁进行气动性能外形优化，并针对关键外形参数的抗风性能参数化分析和评级，满足不同层面的桥梁抗风需求。研究成果将突破和完善现有的桥梁抗风研究基础理论，对大跨度桥梁建设也能提供重要的技术支撑。

箱形主梁在超大跨度桥梁中被广泛应用，随着跨径的不断增长，其气动稳定性能逐渐成为方案设计的关键指标之一。为掌握箱形主梁的风振及制振机理，实现主动地优化箱梁气动外形，本项目结合风洞试验、数值计算以及理论分析方法，系统地研究了扁平闭口箱梁和分体箱梁的涡振与颤振性能随几何外形参数以及气动措施参数的演化规律，主要成果如下：1）基于气动阻尼发展和自由度耦合效应分析理论、气动力做功和能量输入传递分析理论，建立整体气动参数和结构局部分布气动参数间的联系，并结合绕流流场特性，建立宏观和细观层面相结合的桥梁构件抗风性能优化方法；2）基于抗风性能优化方法，分析了闭口箱梁气动稳定性能与风嘴角度、风嘴对称性、开槽率、中央稳定板的布置方式及布置高度、风障的形式及布置位置以及导流板等参数之间的内在机理。3）基于二维与三维颤振分析方法，从初步研究了二维与三维颤振分析结果差异的影响因素以及差异的产生原因，为由二维结构气动优化过渡到全桥结构作铺垫；4）基于大跨度桥梁非线性风致效应全过程的数值模拟平台，探索了桥梁非线性颤振性能与气动外形参数间的内在机理。