基于可靠度理论的桥梁涡激振动概率性评价

PROBABILISTIC EVALUATION OF VORTEX-INDUCED VIBRATION OF BRIDGES BASED ON RELIABILITY THEORY

涡激共振是大跨度桥梁在低风速下容易发生的一种风致振动,涉及的不确定因素众多,利用可靠度理论对这类风致振动进行安全估算是大跨度桥梁风振研究的趋势。探讨了桥梁涡振的三种失效模式,包括基于涡振风速的失效模式、基于涡振振幅的失效模式和基于前两种失效模式交集的涡振刚度失效模式,基于此,以某座大跨度桥梁为例,应用二次四阶矩法计算了基于涡振振幅的失效概率,并与二次二阶矩法的计算结果进行了比较,用Monte Carlo模拟法(MC)进行了验证,发现基于二次四阶矩法的可靠度分析相对于二次二阶矩法具有较高的精度。然后,基于二次四阶矩法的计算结果得到了桥梁涡振刚度失效的概率,研究表明:单独考虑桥梁涡振发生风速或涡振振幅的失效概率偏于保守,应结合起来考虑。

Vortex-induced vibration （VIV） that involves many uncertain factors is an aerodynamic phenomenon that occurs in long-span bridges at low wind speeds. The safety assessment on this kind of wind-induced vibration based on reliability theory is the research trend of long-span bridges. Three failure modes of bridge VIV wind speed, maximum amplitude and VIV stiffness based on the intersections of first two failure modes are investigated Then, a long-span bridge is taken as an example to calculate the VIV amplitude failure probability using a second-order fourth-moment method. The calculation results are compared with those by a second-order second-moment method and verified by Monte Carlo simulation method （MC）. It finds that the reliability analysis based on the second-order fourth-moment method has higher precision than that due to the second-order second-moment method. Afterwards, on account of the calculation result using the second-order fourth-moment method, the probability of bridge VIV stiffness failure is obtained. The investigations illustrate that the failure probability trend is conservative when individually considering the VIV wind speed or the amplitude of a long-span bridge.