Cold Reinforcement Method for Distortion-induced Fatigue Cracks of Steel Bridge

Fatigue cracks seriously affect the safety and service life of steel bridges, and approximately 90% of which are caused by distortion-induced stress. It is urgent to search for an effective reinforcement or strengthening method for distortion-induced fatigue cracks in steel bridges. For this purpose, cold reinforcement methods are developed to reinforce the distortion-induced fatigue cracks in steel bridges, includingdrilling stop holes,bolting angle steel, bonding angle steel and hybrid reinforcement methods. Fatigue tests are conducted on full-scale steel girder models to study the distortion-induced fatigue mechanism and the effectiveness of cold reinforcement methods. Most of distortion-induced fatigue cracks initiate from the web gaps after certain loading cycles, and cold reinforcement methods are carried out when the cracks propagate to a certain length. Test results show that drilling stop hole cannot prevent fatigue crack propagation, but with the other three methods, out-of-plane distortion and stress level decrease sharply, and fatigue cracks further propagation is not observed. Based on experimental study, hybrid reinforcement method issuggested for distortion-induced fatigue cracks reinforcement due to the significant effectiveness and convenient construction.