Dynamic and Fatigue Analyses of Stress Joint for Deepwater Steel Catenary Riser

As the offshore industry continues to progress developments in deepwater, Steel Catenary Riser (SCR) offers great advantages over other risers. In order to provide the hang-off with sufficient stiffness, stress joint is used to connect the riser with platform. When stress joints are located at the top of a deep marine riser, it is greatly affected by both axial and bending stress due to great cyclic loading. So it is necessary to do some research on dynamic and local fatigue analyses for stress joint. In this work, global dynamic analysis for a SCR is performed firstly, then local boundary condition obtained from the previous analysis are applied to the stress joint FE model for time domain dynamic and multiaxial fatigue analysis. Results indicate that the stress level is far lower than yield limit of material and damage induced by fatigue needs more attention. Besides, the damage character of the two types of stress joints differs: for TSJ, the place where stress joint connects with riser is easy to occur fatigue damage; for SSJ, the most probable position is at the place where the end of inner sleeve pipe contacts with the riser body. Compared with SSJ, TSJ shows a higher stress level but better fatigue performance, and it will have a higher material cost. Considering various factors, designers should choose the most suitable type and also geometric parameters