Research On Fatigue Characteristics And Antifatigue Design Of FPSO Topside Module

With the discovery of a large number of deep-sea oil and gas fields,associated oil and gas fields and marginal oil and gas fields,compared with fixed oil and gas exploitation platforms,FPSO has the remarkable characteristics of less investment,short construction period and reusability.The fatigue life of topside module directly affects the service life of FPSO.At present,there is a lack of research on fatigue characteristics of topside module.Based on a FPSO and its load environment,the fatigue characteristics of topside module are analyzed,and the weak links of fatigue are pointed out.The specific research contents are as follows:1)The load of FPSO in the marine environment is analyzed.The motion response equation of ship hull is deduced.The principle of FPSO motion statistical prediction based on wave spectrum is expounded.The RAO of ship hull in each wave direction is calculated by MOSES.The statistic value of acceleration motion response of ship hull is calculated according to wave dispersion diagram.2)The principle of FPSO hull generating hydrostatic bending moment and wave bending moment in water is studied,and the influencing factors of hull girder deformation forcing the topside module to produce deformation are explored.The transient dynamic response of the topside module under different loading and sea conditions is solved by Ansys Workbench.3)The mechanism of fatigue crack and the influencing factors of fatigue life of parts are analyzed.The fatigue analysis method of FPSO topside module is established and the evaluation criterion of fatigue damage is defined.Ansys nCode Design Life is used to verify whether the topside module meets the 25-year design life requirement and locate the fatigue weak links.4)The characteristics and application occasions of various anti-fatigue design methods are analyzed.The fatigue weakness of topside module is improved.The fatigue damage of the improved structure and original structure is compared,which proves that the improved structure can improve the fatigue strength of topside module.Through the research of this subject,the fatigue characteristics and structural improvement methods of the weak links of FPSO topside module are obtained.The key points of overhaul of topside module are pointed out,and the normal production of topside module is guaranteed,which lays a good foundation for the oil and gas exploitation of FPSO,and then drives the development of the whole field of marine engineering and will produce social and economic benefits.