Fatigue reliability of welded steel structures

In general, two different approaches to the formulation of the fatigue limit state are considered, the first based on S–NS–N lines in combination with Miner’s damage accumulation rule, and the second based on fracture mechanics crack growth models and failure criteria. Often, the two approaches are used sequentially, with S–NS–N being used at the design or preliminary assessment stage and fracture mechanics for more refined remaining life or inspection and repair estimates. However, it is essential to link the results, and the decisions made, at the design and assessment stages, and it is therefore important to develop compatible methodologies for using these two approaches in tandem. In doing so, it is essential to understand and quantify different uncertainty sources and how they might affect the robustness of the results obtained, and the subsequent decisions made about the structure. The objective of this paper is to highlight parts of recent research at the University of Surrey on the fatigue assessment of steel bridges. The work includes the development of a probabilistic fracture mechanics methodology for the prediction of fatigue reliability, using up-to-date crack growth and fracture assessment criteria and incorporating information on inspection and subsequent management actions.