Fatigue analysis of box-girder webs subjected to in-plane shear and transverse bending induced by railway traffic

The analysis of slender reinforced concrete box-girder webs, in bridge decks, must be carried out considering the effects of in-plane shear and transverse (out-of-plane) bending. In the case of structures subjected to important cyclic loads, such as railway bridge decks, fatigue must also be taken into account. This paper presents a numerical methodology for fatigue analysis of reinforced concrete girder webs, considering the combined effects of in-plane shear and transverse bending. Fatigue lives are calculated by using the damage accumulation method, which makes it possible to analyse variable amplitude stress histories due to real traffic. The main specificity of the proposed methodology lies in the algorithm for calculation of stress histories in the stirrups and in the web concrete. This algorithm is validated through the comparison with experimental results reported in the bibliography, which demonstrates that the proposed approach provides results on the safe side. The interest and practical consequences of employing this methodology in fatigue analyses of new structures are illustrated through the application to a real case study.