Evaluation on Fatigue Performance of Offshore Steel Structures Considering Corrosion and Residual Stresses

This study investigates the effects of welding residual stresses (WRS) on fatigue performance and corrosion behavior of S355 steel in offshore structures. This study calibrated residual stress measurement coefficients for S355 steel using the hole drilling method (A = -0.39, B = -0.80) and ultrasonic method (acoustic elasticity coefficient K = 6.7), and measured WRS in rib-to-deck welded joints. Results showed longitudinal WRS reached 256.4 MPa and transverse WRS was -105.9 MPa in the weld zone. Fatigue tests demonstrated that untreated specimens failed at 2.4 million cycles, whereas post-weld heat treated (PWHT) specimens showed a 45% longer fatigue life (3.48 million cycles). Corrosion tests indicated WRS increased pitting corrosion, causing 1.16%-1.43% mass loss. The findings demonstrate the detrimental coupling effects of WRS and corrosion, providing critical insights for enhancing offshore steel structures' durability.