Advancement of IIW Fatigue Design Concepts by Applying the Peak Stress Method to Offshore Welded K‐Nodes

Comparing different fatigue analysis techniques is crucial when assessing the structural durability of complex welded structures. The structural stress, notch stress, and crack-propagation concepts were previously applied to the fatigue strength of large-scale welded K-joints commonly adopted in offshore structures under constant and variable amplitude loadings. Here, the K-nodes have been analyzed according to the peak stress method (PSM), which considers the weld toe and weld root as sharp V-notches and estimates rapidly the notch stress intensity factors (NSIFs) using rather coarse FE meshes. A fatigue design stress, the equivalent peak stress, and dedicated fatigue resistance curves are defined in the framework of the PSM, along with software to enable the automated application of the PSM in Ansys Mechanical. The accuracy of each fatigue design concept has been evaluated by comparing the relevant fatigue lifetime estimations with the experimental results. All investigated concepts delivered conservative results, however, with a different ranking.