大跨度桥梁涡激振动强耦合特性的数理模型及其应用研究

Large amplitude oscillation of bridges at relative low wind speeds endangers the safety of bridge users and may cause problems to the fatigue life of structures. The existing theory of bridge wind resistance cannot fully simulate the strong coupling characteristic of fluid-structure interactions during VIV， since the existing framework can only reproduce the weak unsteady and nonlinear features of aeroelastic force while is not able to take its memory effects into account. As a result, an accurate prediction of the prototype VIV response and a reasonable consideration of the influences of actual on-coming flow properties (inhomogeneity or time-variety) on the VIV of a bridge cannot be achieved through the existing framework, as indicated by several practical cases of long-span bridges that experienced VIV after erection. The strong-coupling characteristic of fluid-structure interactions during VIV is to be simulated by using a multidimensional convolution scheme。 The basic premise of this model is that a large class of nonlinear systems can be modeled as a sum of multidimensional convolution integrals of increasing order and the memory effects of aeroelastic forces can be taken into account through the convolution form of this model. Based on this technic and a newly developed forced-vibration facility in wind tunnel, the high precision kernel identification strategy through experiment (the kernel terms are in fact the linear and nonlinear transfer functions between structural motion and VIV forces at different nonlinear order), the modeling and validation of the strong coupling characteristics of fluid-structure interactions during VIV, and the time-domain calculation procedure by combing the multidimensional convolution scheme with the structural finite element method, are going to be conducted. The purpose of this project is to establish a three dimensional time-domain simulation strategy for the VIV of long-span bridges, which can take into account the influences of actual on-coming flow properties. The outcomes of this project, to some extent, will break through the limitations of existing analytical framework of VIV, which may help to improve the theory of bridge wind resistance and guide the design and construction of long-span bridges.

桥梁低风速条件下大振幅振动易引发行人和行车安全事故，并由此衍生结构疲劳损伤等安全隐患。现有涡激气动力理论框架仍然难以准确模拟涡振过程流体-结构间的强耦合特性，仅能简单计入气动力的弱非定常和非线性效应，忽略了气动力的记忆效应。导致现有理论体系难以准确预测实际结构涡振性能，也无法考虑空间非均匀分布、时变等来流状况对涡振效应的影响,引发多起严重的桥梁抗风评估误判工程案例。拟拓展利用新型多维卷积积分模型的数学记忆特性，并充分发挥该模型能够再现时变强非线性效应的特点，构建涡振过程流体-结构间的强耦合关系；完善研发的可按任意指定路径运动的强迫振动装置，实现高精度涡激力模式参数辨识方法；建立多维卷积积分与结构有限元耦合求解策略，实现能够考虑真实来流特性影响的大跨度桥梁涡激振动三维全桥时域模拟。预期成果有望突破现有桥梁涡振分析理论局限，为未来待建超大跨度桥梁提供必要精细化抗风理论基础。

桥梁低风速条件下大振幅振动易引发行人和行车安全事故，并由此衍生结构疲劳损伤等安全隐患。准确评估实际桥梁涡振性能，并依此制定适应的控制方案，是确保大跨桥梁抗风安全与服役性能的关键科学与技术问题。本项目围绕涡振过程流体-结构强耦合特性及涡振全过程时域模拟，开展了3方面工作：（1）主梁涡振系统非线性动力行为及特性：基于弹性悬挂节段模型研究了主梁涡振系统动力稳定及分岔行为，提出了涡振系统动力稳定判定方法。基于弹性悬挂节段模型提出了涡振系统瞬时特性识别方法，准确识别了主梁所受附加气动阻尼、刚度效应。基于强迫振动测试技术，分析了典型断面涡激气动力非定常、非线性特性；（2）流体-结构强耦合特性数理模型：提出了基于主梁非线性附加气弹效应模拟的广义气动阻尼模型，能够一定程度上提升不同质量-阻尼工况结构涡振响应预测精度。提出了基于多维卷积积分的流体-结构强耦合特性模拟方法，对比分析了卷积阶数、内核形式等模型参数对涡激力模拟结果的影响，建立了稀疏和全阶格式的卷积内核识别方法，识别了典型桥梁断面涡激力内核参数，能够有效模拟涡振过程气动力的倍频、时滞等非线性特征；（3）大跨桥梁实桥涡振性能模拟及验证：提出基于广义气动阻尼模型的实桥涡振振幅预测方法，能够预测不同模态（质量-阻尼工况）实桥涡振振幅。基于“弱耦合”算法，建立了多维卷积-结构有限元耦合求解策略，实现了考虑来流展向非一致、时变特性影响的三维全桥涡振时域模拟，并基于现场监测数据验证了该方法的准确性。该方法突破了传统时-频混合格式理论框架仅能针对固定风速开展模拟的局限。