用LES方法对斜拉桥斜拉索风雨振的机理的研究

STUDY ON THE MECHANISM OF RAIN-WIND INDUCED VIBRATION OF CABLES ON CABLE-STAYED BRIDGE USING LES

在特定的风雨条件下,斜拉桥的斜拉索会发生激烈的风雨振现象。这种振动会造成索-梁和索-塔锚固区结构的疲劳损伤等一系列问题,因此,研究并明确斜拉索风雨振的机理,从而找到这种振动的控制方法,已经成为紧迫的研究课题。该文从流场分析入手,利用数值分析的Large-eddy simulation方法,研究了索面存在水线的情况下水线位置不同时流场分布的变化和卡尔曼涡强度的变化,提出水线后侧"小涡"的脱落是影响卡尔曼涡强度的原因。在风速高于卡尔曼涡致振动风速的条件下,当卡尔曼涡受到小涡影响变得足够弱时,索容易发生振动。

Cables on cable-stayed bridges are susceptible to vibration by natural wind because of their low structural damping, especially in rainy and windy days. The vibration of cables can cause a series of problem such as the fatigue damage of anchorage structures. It is important to clarify the vibration mechanism in order to suppress the vibration. In this paper, by using Large-Eddy Simulation method, the flow fields and the Karman vortex intensities of cable with water rivulet at different positions are analyzed. The reasons why Karman vortex intensity is changed by water rivulet are discussed. It is indicated that small vortex shedding behind rivulet can weaken Karman vortex shedding. When wind velocity is higher than the Karman vortex induced vibration velocity and Karman vortex is weakened enough by small vortex shedding, the cables would vibrate.