ABSTRACT
The fatigue analysis of large structures is highly limited by a multiscale problem between the global responses of structural systems and the localised nature of fatigue damage. Currently, S-N curves are used to overcome such an issue using nominal stresses, but overly conservative safety margins may be assumed when investigating existing metallic railway bridges, built and designed using superseded standards. Therefore, advanced numerical analysis consisting of hierarchical models should be performed to implement local fatigue methods based on local mechanical quantities to investigate numerically all fatigue phases, according to the real characteristics of the structural response at fatigue hot spots. The local geometrical, material and contact properties may be accurately represented at the local scale using submodelling relations, potentiated by the implementation of modal superposition principles to increase the efficiency of the calculations. A real case study is investigated in the present work to demonstrate the capabilities of applying local fatigue approaches.
