On the assessment of multiaxial fatigue resistance of welded steel joints in marine structures when exposed to non-proportional constant amplitude loading

Structural geometry and stochastic loads such as swell and wind seas can typically induce multiaxial stress states in welded details of marine structures. It is known that such complex time varying stress states determine the fatigue resistance of welded steel joints. Therefore, it is of importance to account for them in fatigue lifetime assessment. Over the past few decades, a wide variety of design codes and guidelines have been developed for performing fatigue assessments in engineering practice. In particular for multiaxial fatigue lifetime assessment, additional methods have been developed. These multiaxial fatigue methods are typically developed within academia. A consensus on the most suitable approach for the assessment of multiaxial fatigue in marine structures is lacking. This requires thorough investigation of all different approaches, and equitable comparison and validation with experimental data. Establishing a test setup that enables to test multiaxial fatigue of welded marine structures, is however time and cost intensive. Therefore, experimental multiaxial fatigue data is scarce.