Distortion-Induced Fatigue Cracking after Crack Arrest Hole Retrofit of Steel Girder Bridges

The paper presents research on distortion-induced fatigue cracking in steel bridge girders at a connection plate-to-girder web weld toe after retrofit of an original fatigue crack using a crack-arrest hole (CAH). Detailed three-dimensional finite-element analyses (FEAs) of a global model of an example two-girder bridge were used to evaluate fatigue stresses from out-of-plane bending of the girder web in the web gap region before and after the original fatigue crack develops and before and after a CAH retrofit. The local structural stress (LSS) at the connection plate-to-girder web weld toe and the maximum magnitude principal stress (MMPS) on the CAH edge were evaluated and compared to the corresponding fatigue resistance to assess the potential for fatigue cracking. Various original fatigue crack lengths and CAH diameters were studied to determine the influence of these parameters. Results from fatigue tests of specimens that simulate connection plate-to-girder web welds with original fatigue cracks and CAH retrofit under out-of-plane web plate bending were presented. The test results validated the fatigue stress conditions observed in the FEA results and validated the corresponding fatigue resistance for assessing the potential for fatigue cracking.