Evaluation on the Effect of Fabrication Tolerances on the Fatigue Performance of Critical Connections Between Hull Structure and Topsides in Drillship Available to Purchase

With the continuous development of offshore oil and gas resources in deep-water, fatigue has become a major concern for structure safety. It was recognized that the topside and hull interface structures in drillship are critical for the structure integrity. Consequently, a proper estimation of fatigue life for these interface structures is of uttermost importance. On the other hand, at the design and approval stage, the evaluation of fatigue performance is based on assumptions regarding fabrication quality. Most shipbuilding standards include limits on fabrication tolerances such as misalignment, weld profile defect, etc. However, there is little information available on the extent to which these standards area actually met in practice. There is also limited understanding among most designers, builders and owners regarding to the extent to which fabrication tolerances may influence fatigue performance of structures. In this paper, the available data on fabrication tolerances is reviewed and compared to assumptions used in various fatigue analysis standards and guidelines. The impacts of various tolerances on the fatigue life of topside-hull interface structure details are evaluated and the techniques to improve fatigue performances are recommended.