基于性能的π型梁桥涡振响应概率性评价

Performance-based probabilistic evaluation of vortex-induced vibration response ofπ-beam bridges

文章以某π型梁悬索桥为例,采用剪切应力输运(shear-stress transport,SST)湍流模型,基于大变形动网格和有限体积法实现π型截面主梁涡激振动数值仿真;用最小二乘法对阻尼比和竖向涡振最大幅值进行拟合,使用Q-Q图检验阻尼比的概率分布,探究阻尼比与涡振的关系;用设计点法、多种蒙特卡洛(Monte Carlo,MC)法拟合结构随阻尼比变化的损伤曲线,建立桥梁涡振损伤评价框架。研究发现:π型主梁在相当广泛的阻尼比范围存在竖向涡振现象,当阻尼比为5.67×10^(-3)时,主梁的竖向涡振振幅超过限值;阻尼比在每年的8—12月服从对数正态分布,并逐年减小,结构的损伤概率随阻尼比不断减小而增加。文中成功拟合出不同阻尼比下涡振最大幅值、涡振区间的损伤概率曲线,提出基于行车舒适性的桥梁涡振概率性损伤评价方法。研究结果可为π型梁涡振行车舒适度概率性损伤评价提供参考。

This paper aims to investigate the vortex-induced vibration(VIV)of a suspension bridge withπ-beam.Numerical tests of VIV were performed for the bridge deck by using shear-stress transport(SST)turbulence model,large deformation dynamic grid and finite volume method.The relationship between damping ratio and VIV was explored by fitting the maximum magnitude of damping ratio and vertical VIV using least squares,examining the probability distribution of the damping ratio using a quantile-quantile(Q-Q)plot.The damage curves of the structure with the damping ratio were fitted by the design point method and various Monte Carlo(MC)methods to establish a framework for the evaluation of bridge VIV damage.It is found that theπ-beam has vertical VIV in a fairly wide range of damping ratio,and the peak vertical vortex amplitude of the bridge deck exceeds the limit when the damping ratio is 5.67×10^(-3).The damping ratio obeys the lognormal distribution from August to December every year and decreases year by year.Damage probability of the structure increases as the damping ratio decreases continuously.Finally,damage probability curves of the VIV maximum amplitude and interval under different damping ratios were successfully fitted,and the probabilistic damage evaluation method of bridge VIV based on the driving comfort was proposed.The results of the study can provide reference for the probabilistic damage evaluation ofπ-beam VIV based on the driving comfort.