Proposed criterion for fatigue strengthening of riveted bridge girders

Most existing guidelines and recommendations for the fatigue design of riveted members are not considering the effect of stress ratio on the constant amplitude fatigue limit (CAFL). However, fatigue test data show that there is a substantial influence of the stress ratio on the CAFL. In this study, a simple fatigue design criterion for riveted members is proposed taking into account the effect of stress ratio. The applied method is based on the constant life diagram (CLD) methodology. The accuracy of the pro-posed design criterion has been verified using existing test data in the literature. This consideration enables the application of an effective solution for prevention of fatigue failure in riveted members, namely the application of prestressed retrofitting systems, which results in a reduction of the stress ratio. A procedure is therefore presented for the fatigue design of the riveted members strengthened with prestressed and non-prestressed retrofitting systems subjected to constant and variable amplitude loadings. The proposed design procedure is then used in a numerical example to determine the prestressing force and the section modulus re-quired for prevention of fatigue cracking in both the prestressed and non-prestressed retrofitting systems.