Effect of misalignment on fatigue performance of horizontal welded joints in steel catenary riser system

In order to investigate the effect of misalignment on the horizontal girth weld fatigue performance, the joints of steel catenary riser were welded by TIG welding with filler wire and the fatigue tests of the joints were carried out at the stress range of 80, 120 and 175 MPa, respectively. The results indicated that the misalignment mode has a significant influence on the fatigue cracking initiation position of horizontal welding joints. The fatigue crack of upper-misalignment-joint is almost from the upper side of the root toe, and the fatigue crack of joints without misalignment is mainly from the bottom of the root toe, besides, the fatigue crack of down-misalignment-joint is all from the bottom of the root toe. In addition, the fatigue endurance of the specimens is decreased continuously with the increase of the misalignment values at the same stress range, and which is reduced obviously when the misalignment values exceed 0.60 mm.