The inner surface of steel footing got corroded by the unexpected increase in the groundwater level. Its load capacity might be reduced due to the corrosion. FEM analysis was carried out the stiffened plate with a corroded inner surface, then the influence of the corrosion of the panel and the longitudinal stiffener on the ultimate strength was investigated. Especially, this analysis focused on a simple corrosion shape in order to obtain the lower limit of the reduction of ultimate strength. As a result, it was clarified that ultimate strength and deformation mode are different depending on the corrosion rate and shape.
