基于车-桥耦合方法的曲线桥疲劳寿命研究

Research on Fatigue Life of Curved Bridges Based on Vehicle Bridge Coupling Method

摘要:

为了评估混凝土曲线桥梁在多工况影响下的疲劳性能,建立车辆和桥梁两个子系统的振动方程。利用模型接触点的位移协调条件和力学平衡条件建立车-桥耦合振动方程,利用有限元模型模态分析,将一阶频率、二阶频率、耦合模型计算出的跨中挠度位移与实测数据进行对比,校验模型可靠性,考虑温度、车辆行驶速度、桥面不平顺等工况,基于有限元分析软件Ansys进行了车辆荷载作用下混凝土曲线桥动力响应分析,确定了模型疲劳危险点,并获得不同工况下的等效应力数据。根据雨流计数法对应力数据进行统计处理,基于断裂力学理论确定了曲线桥梁主要构件初始裂纹长度、断裂类型、临界裂纹长度、混凝土曲线桥梁裂纹扩展寿命计算方法。研究提出了以疲劳分析为目标的车桥耦合振动响应分析方法、曲线桥梁疲劳剩余使用寿命评估方法,解决了不同工况对疲劳剩余使用寿命的影响等问题。结果表明:裂纹扩展呈现初期缓慢、后期加速的指数型增长特征;车辆行驶位置和温度梯度对疲劳寿命影响显著,而桥面不平顺等级变化影响相对较小。

Abstract:

To evaluate the fatigue performance of concrete curved bridges under the influence of multiple working conditions, vibration equations for the vehicle and bridge subsystems are established. The coupling of the vehicle and bridge vibration equations was established by using the displacement coordination conditions and mechanical equilibrium conditions at the contact points of the model. The modal analysis of the finite element model was used to compare the first-order frequencies, second-order frequencies, and the mid-span deflection displacements calculated by the coupling model with the mea-sured data, to verify the reliability of the model. Considering temperature, vehicle speed, bridge surface irregularity and other working conditions, the dynamic response analysis of the concrete curved bridge under vehicle load was carried out based on the finite element analysis software ANSYS, and the fatigue hazard points of the model were determined, and the equivalent stress data under different working conditions were obtained. The stress data were statistically processed using the rainflow counting method, and the initial crack length, crack type, critical crack length, and calculation method for the crack propagation life of the concrete curved bridge based on the fracture mechanics theory were determined. The study solved the problems of the vehicle-bridge coupled vibration response analysis method for fatigue analysis, the fatigue remaining service life assessment method for curved bridges, and the influence of different working conditions on the fatigue remaining service life. The results show that the crack propagation presents an exponential growth characteristic of initial slow and later accelerated; the vehicle driving position and temperature gradient have a significant impact on the fatigue life, while the change in bridge surface irregularity level has a relatively smaller impact.