Fatigue strength of shot-peened welded joints of steel bridges

This study aims to determine the fatigue strength of shot-peened welded joints, thus including an implementation case study based on existing bridges and an investigation of the influence of coverage conditions on fatigue strength based on specimens. The case study involved performing field residual stress measurement with the X-ray diffraction method and comparing it with another existing bridge and specimens. The comparison result indicated that the shot peening for the existing bridges was verified to the stable introduction of compressive residual stress in the weld toe. The influence of different conditions, 90%, double 90%, or triple 90% coverages, on the fatigue strength was clarified by residual stress, weld geometry measurements, and fatigue tests at R = - 1. From those works, the shot peening for more than double 90% coverage might be needed for stable treatment. This treatment can ensure compressive residual stress of more than 80% of the material yield strength at 100-mu m depth near the weld toe and achieve as high fatigue strength as HFMI treatment. Moreover, weld toe geometry might be improved as the coverage increases. Besides, the fatigue design curve of FAT90 for HFMI treatment in IIW recommendations might be applied to shot-peened welded joints.