For steel girder reinforced by one side patch plate with high strength stud bolts, reinforcement effect and the effect of patch plate connection structure had been confirmed, but it is unclear on fracture behavior of reinforcement section. In this study, experiment of steel girder repaired the lower flange subjected to bending had been carried out. The load-carrying capacity of steel girder reinforced with high strength stud bolts is equivalent to that of the high strength bolts, because the relationship between load and displacement, strain distribution on the reinforced section are roughly match the design. It is understand that yielding occurred on the lower flange at the maximum bending position, slipping occurred on the end of patch plate.
