Fatigue strength degradation of corroded structural details: A formula for S-N curve

A formula is proposed to predict fatigue strength of corroded members and joints of steel structures. The concept of the formula is first studied from recently identified mechanism of corrosion fatigue. Hence, the corresponding fatigue strength curve (i.e. S-N curve) of corroded steel is presented. It is further improved to derive linear, bilinear or trilinear S-N curve for corroded constructional details of steel structures. The parameters of the corroded steel S-N curve are determined based on the corrosion fatigue testing results of different types of steel specimens in air, fresh water and seawater. Hence, the parameters for the derived S-N curve of corroded constructional details are predicted based on the above parameters and tabulated for the detail categories given in the Eurocode and DNVGL code. The proposed S-N curve formula is compared with full-scale fatigue test results of several constructional details, and the validity of the formula is confirmed.