Abstract: A whole bridge model and node sub-model of simply supported steel truss bridge were established by the finite element analysis method. The correctness of the finite element model was verified by comparing the measured values with the calculated values of the finite element method of the key section vertical displacement and the axial stress of the member. The variation rules of stress intensity factors KⅠ, KⅡ, and KⅢ at the crack tip under different crack lengths were analyzed. Aimed at fatigue cracking of web gap in crossbeam joints, the maintenance effects of cutting the upper flange and angle steel reinforcement were analyzed. A combined maintenance method of cutting the upper flange of the beam end and strengthening the angle steel was proposed. The results show that the cracking mode changes from type Ⅱ-Ⅲ crack to type Ⅰ-Ⅱ-Ⅲ crack and then to type Ⅱ-Ⅲ crack during the whole process of crack propagation. The upper flange cutting method and angle steel reinforcement method have good repair effects on both type I and type Ⅱ cracks, and the combined maintenance method of the upper flange cutting and angle steel reinforcement has a good inhibitory effect on composite type cracks. In the proposed model, when the crack propagation length is less than 60% of the web gap length, the equivalent stress intensity factor at crack tip can be reduced by 60% to 90%, and the inhibiting effect is significant.

Key words: bridge engineering; steel truss bridge; web gap; fatigue cracking; stress intensity factor

摘要： 采用有限元法建立了简支钢桁梁桥全桥模型及节点子模型；通过对比关键截面竖向位移及杆件轴向应力的实桥测试值与有限元计算值，验证了有限元模型的正确性；分析了不同裂纹长度裂纹尖端的应力强度因子KⅠ、KⅡ、KⅢ的变化规律；针对横梁节点腹板间隙疲劳开裂，分析了上翼缘切削方法及角钢加固方法的维修效果；提出了横梁端部上翼缘切削与角钢加固的组合维修方法。结果表明：裂纹在整个扩展过程中，开裂模式从Ⅱ-Ⅲ型开裂先向Ⅰ-Ⅱ-Ⅲ型开裂转变，再向Ⅱ-Ⅲ型开裂转变；上翼缘切削方法、角钢加固方法对Ⅰ型裂纹、Ⅱ型裂纹均具有较好的维修效果，组合维修方法对复合型裂纹具有较好的抑制作用；模型中当裂纹扩展长度小于腹板间隙长度的60%时，裂纹尖端等效应力强度因子可降低60%～90%，抑制效果显著。

关键词: 桥梁工程；钢桁梁桥；腹板间隙；疲劳开裂；应力强度因子