In steel railway bridges with open deck system, the local buckling of compressive flanges under sleepers on plate girders caused by the local corrosion of flanges leads to the collapse of bridges. The local corrosion is thought to have a substantial impact on the ultimate strength of main girders. However, past research on ultimate strength contains few inquiries into the relationship between the local corrosion of compressive flanges and the ultimate strength of main girders, and a method of evaluating the relationship has not yet been established. In this study, parameter analyses that focus on plate girders with local corrosion under sleepers have been conducted by using full-scale plate girder models subjected to bending and local loads simultaneously. Then based on these analytical values and other existing experimental values, the study verified the applicability of the separate evaluation equations that we previously proposed for remaining load bearing capacity under bending and local loads respectively, as well as the remaining strength calculation method based on the strength interaction curve of plate girders subjected to bending and local loads simultaneously to clarify that ultimate strength can be evaluated with a high degree of accuracy.