INTERNALLY RING STIFFENED TUBULAR JOINTS: SALVATION OR STRUCTURAL LIABILITY?

As the second phase of the United Kingdom Offshore Steels Research Project, large scale fatigue tests on internally stiffened tubular welded joints have been carried out at the National Engineering Laboratory. Tubular joints in the T configuration have been fatigue tested in air under constant amplitude loading conditions. The results, when presented in the conventional S-N format where S is the applied hotspot stress range and N is the number of cycles to failure, suggests the introduction of heavy stiffening is detrimental to fatigue life while light stiffening enhances fatigue life, when compared with tubular joints of similar geometry with heavier chord section thickness. The unconventional failures experienced by the joints in this investigation cast doubts on the applicability of the hotspots stress approach to ring stiffened tubular joints. See next Abstract.