正交异性钢桥面板双轴疲劳性能评估

Biaxial Fatigue Behavior Evaluation of Orthotropic Steel Deck

为精确评估正交异性钢桥面板在双轴应力状态下的疲劳性能,以东营胜利黄河大桥为背景,建立该桥正交异性钢桥面板顶板、U肋、横隔板交叉连接部位焊缝的节段三维有限元模型,采用等效结构应力法对正交异性钢桥面板体系的双轴疲劳问题进行研究;通过模型试验验证正交异性钢桥面板体系的双轴疲劳特性,并进行其构造细节疲劳寿命评估。结果表明:弧形切口起焊点的疲劳裂纹萌生位置在横隔板下方焊趾处,经历裂纹萌生、裂纹稳定扩展和裂纹失效3个阶段,最终失效阶段裂纹形式为Ⅱ型裂纹主导的Ⅰ-Ⅱ型复合裂纹,此为该桥正交异性钢桥面板结构体系的主导疲劳失效模式;顶板焊缝焊趾及弧形切口起焊点焊趾处于双轴应力状态,面内剪切结构应力幅对疲劳应力的影响显著,按单轴疲劳应力进行寿命预测误差较大,按单轴疲劳应力状态对结构进行疲劳寿命设计偏于不安全;基于组合等效结构应力法的计算值与试验值吻合较好,各焊接细节计算得到的最大值下的疲劳裂纹起裂位置均与试验结果一致,按双轴疲劳应力预测疲劳寿命与试验值吻合较好,疲劳寿命评价精确度较高。

This study investigates the fatigue performance of the orthotropic steel deck under biaxial stresses.The 3D finite element model of an orthotropic steel deck involving the welded joints of the top plate,U ribs and diaphragms was developed based on the Shengli Huanghe River Bridge in Dongying,and the biaxial fatigue performance of the orthotropic steel deck was analyzed using the equivalent structural stress method.Model tests were conducted to verify the numerical simulation and predict the fatigue life of the welded joints.It is shown that cracks at the welding initiation points of the arc cut-outs start from the welding toes underneath the diaphragms,undergoing a conceiving,propagating and failure stages,and at the failure stage,the cracks are theⅠ-Ⅱmix cracks,with theⅡ-cracks play a dominant role,which are also the primary fatigue failure modes of the orthotropic steel deck system.The welding toes of the top plate and the welding toes at welding initiation points of the arc cut-outs are in biaxial stress state,the in-plane shear stresses are significantly associated with fatigue stresses,when using the uniaxial fatigue stresses to predict fatigue life,there would be great errors,thus it is not proper to use uniaxial stress state in the fatigue life design.The fatigue life calculated by the combined equivalent structural stress method agrees well with the test result,and the crack initiation points determined using the maximum calculated values of each welded joint are also in agreement with the test results.The fatigue life predicted using biaxial fatigue stresses agrees well with the test result,with high prediction accuracy.