Probabilistic Fatigue Assessment of Welded Joints

A methodology for probabilistic fatigue assessment of welded joints using the S-N and fracture mechanics approaches is proposed. A fatigue crack propagation model is presented for a semi-elliptical crack in a welded plate which accounts for the effects of weld geometry, residual stresses, stress ratio, fatigue threshold and variable amplitude loading. A simple lognormal format and a rigorous FORM/SORM approach is used for evaluating the reliability of a joint against failure by fatigue. The model accounts for the uncertainties in fatigue loading, stress analysis, stress intensity factors, initial defect size and crack growth material properties. Examples involving reliability analysis of tubular joints of offshore structures are presented.