Retrofit against fatigue cracking at web penetration details with a slot in steel girder

Fatigue cracking in steel girder web penetration details is so dangerous that it can break steel girders. The purpose of this study is to clarify fatigue behavior of web penetration details with cross beam flange welded to upper or lower surface of a slot by fillet welding, and verify the effect of retrofitting methods against fatigue cracking in web penetration details. As a result, fatigue cracks were initiated at the web-side toe of the fillet weld along cross beam lower flange edges both in upper and lower welded specimen. In the upper welded specimen, fatigue cracks were propagated into the web plate diagonally upward almost perpendicularly to the maximum principal stress direction. Whereas in the lower welded specimen, fatigue cracks were propagated into the web plate vertically downward faster than in the case of the upper welded specimen, and broke the lower flange. The fatigue life of the lower welded specimen was shorter than that of the upper welded specimen. As a preventive measure, weld toe grinding can extend fatigue life a little, but cannot prevent crack initiation perfectly. As a post cracking measure, a stop hole can stop crack propagation of long cracks, whereas crack removal and shaping up method by grinding can prevent crack propagation of short cracks.