فرسودگی چند محوره اتصالات جوش داده شده
Abstract
1-Introduction
2-Description of railway steel bridge
3-Fatigue load models
4-Numerical modelling of bridge
5-Fatigue damage assessment
6-Results
7-Conclusions
Acknowledgements
References
Abstract
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.
Introduction
Due to enhanced demand in Reliability, Availability, Maintainability and Serviceability (RAMS) of structural systems, there is an increase in demand to understand and estimate the precise fatigue damage in bridges. An advanced fatigue design methodology is required to recognize potential critical details introduced by specific design changes. So far, there is no precise and robust fatigue damage estimation tool particularly for welded details. Especially in bridges, stresses developed at welded connections are always multiaxial and non-proportional. Fatigue assessment based on the critical plane approach is generally accepted to be more accurate for multiaxial nonproportional loading. There are several multiaxial fatigue damage models in the literature which propose different damage parameters. In general, critical plane models require scanning over all planes intersecting the surface either orthogonally or at some inclination for maximum value of damage parameter. Also, the stress analysis has to be performed for each time step considered in the simulation of the train crossing. This complex and cumbrous task is simplified in the C-S criterion by applying some weight functions and linking the critical plane with mean principal stress directions.