桥梁吊索高强钢丝疲劳裂纹扩展试验与数值模拟

Experimental and Numerical Study on Fatigue Crack Growth of Bridge Suspender

反复车辆荷载作用下,斜拉桥斜拉索及拱桥吊杆疲劳损伤问题日益严重。针对大跨桥梁中常用的镀锌高强钢丝,开展了应力比R分别为0.1、0.2、0.3的疲劳裂纹扩展试验,研究了应力比及应力幅对钢丝疲劳裂纹扩展性能的影响,每种应力比下的应力幅分别为140.4、152.1、163.8、175.5MPa。采用分步加载方法,设计不同加载应力幅在试件断裂面留下裂纹扩展时的条纹特征,利用光学显微镜对疲劳断口的疲劳条纹进行观测,得到了不同应力比下裂纹扩展深度与疲劳循环次数的a—N曲线,拟合了高强钢丝的疲劳裂纹扩展速率模型。试验结果表明:钢丝疲劳裂纹呈三阶段扩展,随着应力比R的增大,Paris公式中参数C变小,m变大。运用有限元软件ABAQUS模拟了裂纹扩展过程,定量分析了裂纹扩展径向与表面方向的关系,试验结果与有限元结果吻合较好。试验得到的疲劳裂纹扩展速率曲线,可用于大跨桥梁吊索的抗疲劳、防断裂设计及疲劳寿命评估。

The fatigue damage for cable-stayed bridge cable and arch bridge hanger become serious under cyclic loadings.The fatigue crack growth tests for galvanized high strength steel wires that are widely used in large-span bridges were performed with stress ratios of R=0.1,0.2 and 0.3.The effects of stress ratio and stress amplitude on the fatigue crack propagation of steel wires were studied,and four stress amplitudes were considered,i.e.140.4 MPa,152.1 MPa,163.8 MPa and 175.5 MPa.A two-step loading method was selected in the tests.Fatigue stripes were presented in the fracture surface using different loading amplitudes,and the stripes of the fatigue fracture were observed by an optical microscope.The a-Ncurves related to the crack propagation depth and the fatigue cycles under different stress ratios were obtained.The curves of fatigue crack propagation rate of the steel wires under different stress ratios were also fitted.The experimental results show that fatigue crack propagation exhibited three stages.As stress ratio increases,the parameters C in Paris formula decreases and the parameter m increases.The crack propagation process was simulated by the finite element software ABAQUS,and the relationship between the radial direction and the surface direction of crack growth is quantitatively analyzed.The experimental results are in good agreement with the finite element simulation results.The obtained curves of fatigue growth rate can be used for fatigue design,fracture control and fatigue life assessment for existing large-span bridge suspender.