Repair of the bottom flange in steel I-girders caused by corrosion is generally repaired by patch plates with high-strength bolt friction joints. However, the stress in the corroded flange in steel I-girders repaired by patch plates subjected to bending does not correspond with that calculated using the composite theory of cross-section of corroded steel I-girder and patch plates. Therefore, this study proposed a simple estimation method of the shared cross-sectional forces of steel I-girders repaired by patch plates using shear lag theory. The proposed equation can estimate the shared sectional forces with the same degree of accuracy as the results of FEM analysis.
