钢箱梁疲劳裂纹气动冲击法维修效果评估

Evaluation of fatigue crack repairing effect by pneumatic impact method in steel box girder

以实桥疲劳裂纹为研究对象,从应力和应力强度因子角度评估气动冲击维修方法的现场实施效果.对维修前后疲劳裂纹尖端附近的应力分别进行24 h数据采集,并采用雨流计数法,探讨裂纹尖端应力幅的变化规律.结合应力强度因子测试理论,对比研究裂纹尖端应力强度因子幅的变化规律.研究结果表明:本测点疲劳裂纹为典型的Ⅰ-Ⅱ复合型裂纹,维修后疲劳裂纹尖端张拉和剪切应力幅均得到有效降低,改善了裂纹尖端受力条件.高应力强度因子幅的循环次数显著降低,表明气动冲击维修技术对于制约复合型裂纹扩展具有良好效果.

The retrofitted effect of pneumatic impact method was evaluated by both stress and stress intensity factor(SIF)based on the fatigue cracks in real-world bridge.The daily(24 h)stress near the fatigue crack tip before and after pneumatic impact repairing was collected,and the stress amplitude distribution was determined through the rain-flow counting method.The variation of SIF amplitude at the crack tip,was compared and investigated according to the SIF testing theory.The results showed that the fatigue crack at the test point was a typical I-II mixed mode crack.Both the values of tensile stress amplitude and shear stress amplitude at the fatigue crack tip decreased after repairing,indicating that the stress condition at the crack tip was improved.The numbers of high SIF amplitude were reduced,indicating that the pneumatic impact method had a good effect on restraining the propagation of mixed mode crack.