Multiaxial Fatigue Damage Assessment of Welded Connections in Railway Steel Bridge using Critical Plane Approach

As the number of heavy railway traffic load increased, concern over the accurate and actual fatigue damage of the bridge is intensified. Especially for bridges which were designed for light traffic load. The fatigue damage assessment of steel bridge connections is usually based on notion of uniaxial S-N curves given in the codes of practice. Until now, there is no consensus on a method which can precisely consider non-proportional multiaxial loading. The objective of this paper is to examine the applicability and appropriateness of the critical plane approach-based C-S criterion to perform the fatigue damage assessment in welded connections in railway steel bridge. A regular U trough railway steel bridge is analyzed using finite element software ANSYS 17.2 for standard railway traffic. The averaged principal stress directions determined through appropriate weight functions are used to orient the critical plane. Prediction of fatigue damage is performed through an equivalent stress represented by a quadratic combination of the normal and the shear stress components acting on the critical plane. Applicability of the C-S criterion is studied by assessing the fatigue damage of critical welded connections and comparing with the λ - coefficient and cumulative damage method calculated according to Eurocode EN1993-1-9.