基于断裂力学的钢桥面肋-板接头疲劳寿命预测

摘要

为研究反复荷载作用下正交异性钢桥面中U型肋与桥面板焊接接头的疲劳性能,基于断裂力学基本理论,利用有限元方法,进行了肋-板接头的疲劳寿命评估.根据正交异性钢桥面与U型肋连接构造基本形式,利用有限元软件ANSYS建立了包含3个U型肋的正交异性钢桥面平面有限元模型;考虑肋-板连接位置处焊接细节的4种典型裂纹,计算了2个加载工况下各裂纹处等效应力强度因子,并分析了初始裂纹长度、桥面板厚度、U型肋高度和U型肋厚度对等效应力强度因子的影响规律;依据Eurocode 3规范中正交异性钢桥面肋-板接头加载模式,采用桥面板与U型肋连接构造二维有限元模型,计算得到典型裂纹的等效应力强度因子,建立了基于断裂力学疲劳扩展模型为基础的正交异性钢桥面肋-板接头的疲劳寿命预测方法.研究结果表明:基于线弹性断裂力学原理计算得到的疲劳寿命均大于Eurocode 3规范计算值,桥面板厚度选用16～18 mm及将初始裂纹长度控制在0.1 mm以下可有效地提高板-肋接头疲劳寿命.%In order to explore the fatigue performance of U-shaped fib-to-deck welded joints of orthotropic steel bridge deck under cyclic loading,based on linear elastic fracture mechanics (LEFM),fatigue life evaluation was carried out using finite element method (FEM).According to the structure features of rib-to-deck welded joints of orthotropic steel bridge deck,2D FEM model with 3 U-shaped fibs was built using ANSYS software.Presetting 4 kinds of initial cracks for weld detail,the equivalent stress intensity factors (ESIF) at each crack with 2 loading cases were calculated.The relationship between stress intensity factor and influential parameters,including initial cracks length,thickness of deck plate,height and thickness of U-shaped rib,was analyzed.In accordance with weld detail category of orthotropic steel bridge deck in Eurocode 3,ESIF at every crack were obtained,and fatigue life prediction method of weld joint of orthotropic steel deck were proposed based on fatigue crack propagation model in LEFM theory.Results show that fatigue life calculated with LEFM is greater than the value in Eurocode 3,and fatigue life of the welded joint will be enhanced when the deck plate thickness is 16-18 mm and initial crack length is less than 0.1 mm.