ABSTRACT
Corrosion and fatigue are main deterioration factors to control durability of steel bridges. Hence if we control corrosion and fatigue, it is easy to improve durability. When corrosion and fatigue act at the same time, we call it corrosion fatigue. It is well- known as declining fatigue strength sharply. Principal results obtained through this study are as follows. (1) In the crack occurred from corroded depressive parts, fatigue strength was about category B of the old standard. (2) In cracks occurred from edge parts of cross-section loss, fatigue strength was about C of the old standard. we consider that these cases are about category C. These cases are one category lower than the case what the crack occurred from corroded depression. We consider this reason that degrees of stress concentration are difference between shapes of corroded depression and corroded loss parts of edges.
