In this study, we investigated countermeasures using repair welding for fatigue cracks that occurred near the supports of an I-beam bridge made from aged steel. First, we conducted weld cracking tests based on the repair welding that the authors are considering for six types of aged steels produced in different years, and verified the weldability of the aged steels using the results of chemical composition analysis. We also conducted fatigue tests on a full-scale test specimen made in 1927 after repair welding to confirm the effectiveness of the repair. Furthermore, we conducted fatigue tests on a small test specimen simulating repair welding, and verified the applicability of the full-scale test specimen using the obtained fatigue strength curve.
