基于滑移理论的斜拉索风雨激振致振机理研究

Rain-wind induced vibration (RWIV) is the phenomenon that stay cable may vibrate with large amplitude and low frequency under the special conditions of wind and rain, which may cause fatigue damage of stay cable. As RWIV is a very complex problem of coupling oscillation of gas, liquid and solid, its mechanism is still unclear so far. According to the 2D section model of RWIV established by the project team previously, 3D water film evolution equations of rigid cable and flexible cable are derived respectively in this project, which are based on lubrication theory and combined with computational fluid dynamics (CFD), water film thickness measuring experiment and section flows testing experiment of 3D rigid cable. The 3D mathematical models of RWIV that can simulate the morphology variation of water film around cable under wind and rain are also established by coupling water film evolution equations and cable vibration equations. To reveal the mechanism of RWIV, the relationships between water film morphology, aerodynamic force and vibration of cable, and the effects of axial flow and axial vortex on RWIV are all investigated by these 3D models. Further more, the influence rules of meteorological conditions and cable properties on RWIV are also analysed, which may provide theoretical guidance and technical support for the application of damping measures, and also safety guarantee for bridge operator.

风雨激振是指斜拉桥斜拉索在特定风雨条件下的低频、大幅度振动，会引发斜拉索的疲劳破坏。由于风雨激振涉及气、液、固三相耦合问题，国内外至今尚未明确其产生机理。为研究斜拉索风雨激振的产生机理，本项目基于滑移理论，在项目组前期已建立的二维断面模型基础上，结合人工降雨条件下的刚性节段斜拉索表面水膜厚度测试试验、断面流量测试试验及计算流体力学，建立三维刚性节段斜拉索和柔性斜拉索表面的水膜运动方程，并通过与斜拉索振动方程相耦合构建能够模拟风雨激振过程中的斜拉索表面水膜（水线）形态变化的三维斜拉索风雨激振数学模型；应用此模型从水膜形态变化、斜拉索振动与气动力变化间的相互作用及轴向气流、轴向涡对风雨激振的影响这两方面揭示风雨激振的产生机理，并分析气象条件和斜拉索自身属性对风雨激振的影响规律，为各种减振措施的应用提供理论指导和技术支持，为桥梁运营提供安全保障。

风雨激振是指斜拉桥斜拉索在特定风雨条件下的低频、大幅度振动，会引发斜拉索的疲劳破坏。由于风雨激振涉及气、液、固三相耦合问题，国内外至今尚未明确其产生机理。为研究斜拉索风雨激振的产生机理，本项目基于滑移理论，在项目组前期已建立的二维断面模型基础上，结合人工降雨条件下的刚性节段斜拉索表面水膜厚度测试试验、断面流量测试试验及计算流体力学，建立三维刚性节段斜拉索和柔性斜拉索表面的水膜运动方程，并通过与斜拉索振动方程相耦合构建能够模拟风雨激振过程中的斜拉索表面水膜（水线）形态变化的三维斜拉索风雨激振数学模型。应用MATLAB软件进行编程，并对相关程序进行优化设计，高效率的完成上述模型的数值计算。通过对比三维柔性斜拉索模型、三维刚性节段斜拉索模型及已有的二维斜拉索断面模型的数值计算结果，从水膜沿斜拉索轴向形态变化、柔性斜拉索垂度及振动模态对风雨激振影响等方面评价本项目构建的数学模型的有效性和合理性。应用此模型从水膜形态变化、斜拉索振动与气动力变化间的相互作用及轴向气流、轴向涡对风雨激振的影响等方面揭示风雨激振的产生机理，发现当拉索发生风雨激振时，拉索表面水线沿着环向发生周期性振荡，其振荡周期与拉索自振频率相接近，且上水线的环向振荡位置与斜拉索横风向振动位置时程相比存在1/4周期左右的相位差，说明水线与拉索之间的共振是风雨激振产生的原因之一。在此基础上，分析气象条件和斜拉索自身属性对风雨激振的影响规律，为各种减振措施的应用提供理论指导和技术支持。本项目建立的三维斜拉索风雨激振数学模型及其数值求解方法可用于斜拉索风雨激振气动减振措施的开发和研究，为桥梁运营提供安全保障。