Deep-water tendon and riser systems are often subjected to severe fatigue loading from waves, currents and vessel movements. The girth welds between successive lengths of pipe or at pipe terminations represent fatigue-critical features where failure would be catastrophic. Hence, validation fatigue testing by full scale pipes of the most critical welds are often performed to ensure adequate quality and/or to document a better S-N curves than those available in standards today like DNVGL-RP-C203 [1] and BS7608 [2]. To better understand the fatigue performance with respect to identify trends, dependencies and critical features that influence the fatigue performance, a JIP on Fatigue of Girth Welds were initiated in 2011. Two phases have been conducted and a total of 1700 full scale one sided girth welds, mostly run by Stress Engineering, have been statistically analyzed. The test data has been interrogated to investigate the effect of as-welded condition, OD ground, OD/ID ground, un-reeled pipe, reeled pipe, thickness and effect of misalignment. Based on these analyses, new S-N curves for risers and pipelines have been included in DNVGL-RP-C203 for non-reeled girth welds. This paper presents the findings and trends from the JIP work which has been the rationale for the updates of girth welds in section 2.10 in DNVGL-RP-C203 2016 edition.

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