基于应变能的纵肋与横肋连接多轴疲劳评估方法

Multiaxial Fatigue Evaluation Method for Rib-to-diaphragm Welded Joints Based on Strain Energy

为准确评估正交异性钢桥面板结构中纵肋与横肋连接构造的疲劳性能,从疲劳开裂的本质特征出发,以改进的应变能密度为参量,考虑多轴效应对疲劳性能的影响,推导并建立了基于改进的应变能密度疲劳性能评估方法,评估了焊接复杂部位在多轴应力状态下的疲劳性能。在此基础上,针对纵肋与横肋连接部位,以港珠澳大桥正交异性钢桥面板足尺节段模型疲劳试验为研究背景,将模型试验结果与所推导的公式计算结果进行对比,验证提出方法的适用性和准确性。研究结果表明:对于正交异性钢桥面板而言,纵肋与横肋连接构造部位为典型的多轴受力状态,多轴效应对其疲劳性能的影响不可忽略;计算所得单轴应变能密度略小于理论值,只考虑单轴效应对该部位进行疲劳寿命评估会导致偏于不安全的结果;而以总的弹性应变能密度为参量,将导致计算结果偏大,寿命评估结果偏于保守;基于多轴应力的改进能量法计算结果与理论值能较好吻合,且最大相对误差为9.7%;所提方法能适用于正交异性钢桥面板横肋与U肋连接部位疲劳性能评估。

In order to evaluate the fatigue performance of rib-to-diaphragm connection of orthotropic steel deck（OSD）accurately,the fatigue performance evaluation method based on modified strain energy was derived and established,fatigue performance at the complex welded details under multiaxial stress state was evaluated,based on the essential characteristic of fatigue cracking,taking modified strain energy density as parameter and considering the influence of multiaxial effect on fatigue performance.Then,the full-scale segment model fatigue test of OSD of Hong Kong-Zhuhai-Macao Bridge was taken as research object,the application and accuracy of the proposed method were validated by comparing the model testing data and the results calculated by the derived formulate.The results show that the rib-to-diaphragm connection detail of OSD is in a typical multiaxial stress state,and the multiaxial effect on fatigue performancecannot be ignored.The uniaxial strain energy density by computing is less than theoretical data,and the consideration of uniaxial effect on the fatigue life evaluation can lead to insecure results.However,the evaluation method adopting total elastic strain energy as parameter will get larger calculated results and lead to conservative evaluation result in evaluating fatigue life.The results of modified energy method in multiaxial stress state will be in well agreement with theoretical values,and the maximum relative error is 9.7%.Therefore it is a feasible way to evaluate the fatigue performance of the rib-to-diaphragm connection details of OSD by the proposed method.