Probabilistic Approach to Fatigue Assessment for Stay Cables

In structures submitted to repeated variable loads, initiation and growth of cracks in the material are one of the most common causes of the deterioration of structures, especially in combination with corrosion. Under variable amplitude and repeated loads, some local cracks initiate on critical points of the structures, develop into critical cracks and failure due to fatigue. Many parameters used for predicting times to failure of structure due to fatigue are uncertain and their variations have a big influence on the real lifetime. This paper will focus on a global methodology to take into account main sources of variability in fatigue prediction for stay cables in cable stayed bridges. The first step of this methodology is to model the variability of each parameter. Loading is one of the most important sources of variability. Another important source of variability is the fatigue strength of the material. Probabilistic Wöhler curves are fitted using available data, and used to represent the variability of material fatigue behaviour. Finally, the reliability is assessed using Monte Carlo simulations.