基于非齐次复合Poisson过程的正交异性钢桥面板细节疲劳裂纹随机扩展研究

传统的正交异性钢桥面板疲劳损伤评估常采用确定性和可靠性分析方法,忽略了疲劳裂纹扩展的随机性影响,针对这一问题,提出钢桥面板细节疲劳随机扩展分析方法。本文以南溪长江大桥为工程背景,基于长期车辆荷载监测数据,建立了车辆荷载非齐次复合Poisson过程模型。建立钢桥面板有限元模型,采用瞬态分析方法将随机车辆荷载转化成细节疲劳应力,基于线弹性断裂力学理论推导U肋-顶板焊接细节疲劳裂纹扩展时变微分方程,实现宏观关系式疲劳应力幅次数-疲劳损伤至微观表达式应力时间序列-疲劳损伤转换,讨论了车载次序及超载对疲劳裂纹扩展的影响。研究结果表明,非齐次复合泊松过程模型能够较好描述随机车流运营状态,车辆荷载的次序对疲劳裂纹扩展速率的影响不可忽略,重车排序靠前时能够促使疲劳裂纹扩展增速,南溪长江大桥细节点的车辆超载迟滞效应修正系数取值0.804。

Fatigue crack stochastic growth assessment of the orthotropic steel bridge deck based on Nonhomogeneous compound Poisson process model

The traditional fatigue damage assessment of orthotropic steel decks (OSD) commonly used deterministic and reliability analysis methods.The effect of stochastic fatigue crack propagation was ignored.For this reason,the article proposed a new stochastic fatigue crack propagation analysis method for OSD welds.Taking Nanxi Yangtze River Bridge as the project background,the non-homogeneous compound Poisson process model for the vehicle load was established based on the long-term vehicle load monitoring data.The finite element model of a steel bridge deck was established.Then,the OSD fatigue stresses under the vehicle loading were analyzed using a transient analysis.The time-varying differential equations for fatigue crack propagation from U rib to deck were derived based on the linear elastic fracture mechanics theory.Then,the macroscopic relationship fatigue stress amplitude times-fatigue damage was converted to the microscopic relationship stress time series-fatigue damage.The influences of vehicles order and overload on fatigue crack propagation are discussed.The research shows that the nonhomogeneous compound Poisson process model fit the operation state of random traffic flow well.The loading sequence is influential,for example,crack propagated faster when the higher vehicle load was at the front of a vehicle sequence.An overload correction factor of 0.804 is proposed for the Nanxi Yangtze River Bridge.