Comparative Study on Fatigue Analysis Methods using Turret-moored FPSO Model

Ozgur Ozguc

Abstract

Abstract Floating structures are prone to fatigue due to high cyclic loads mainly caused by waves and changing loading conditions. Therefore, fatigue is an important criterion during design. The fatigue life is dependent upon factors such as global and local design, workmanship during construction, maintenance, corrosion protection, and trade and load history. Different approaches are applied to the fatigue strength assessment. Longitudinal stiffener end connections are also important structural elements in the hull structure of ships, floating production storage and offloading units (FPSOs), semisubmersibles and tension leg platforms. Further the wave loads introduce significant dynamic stresses in the side shell below the mean water level. This has led to a number of fatigue cracks in the welded connections between side longitudinal stiffeners and transverse frames and bulkheads of hull structure. The objective of this paper is to perform the comparative study between full stochastic fatigue analysis methodology and DNVGL load component stochastic fatigue methodology using the calculated fatigue life of longitudinal members amidships. A turret-moored FPSO is used as a case study. These fatigue calculations should also be used as guidance for close-up inspections. Advantages and limitations of the different fatigue design approaches are discussed based on results from the case study. Keywords: Fatigue design, S-N curves, FPSO hull structure, Finite element analysis, Turret mooringCite this Article Ozgur Ozguc. Comparative Study on Fatigue Analysis Methods using turret-moored FPSO model. Journal of Offshore Structure and Technology. 2016; 3(3): 1–15p.