Fatigue Analysis Of FPSO

Traditionally, ship structures are designed in conformity with ultimate loads. While, along with the wide-spread application of high strength steel(HSS)and the improvement of weld ability. The strength of ship structures improve greatly, which can minimize and lighten structures members. Although HSS application to ship structure may decrease the expenses of construction and operation,the stress level in the structures will increase accordingly. As a result, fatigue strength becomes one of the most significant problems in ship structures, which is worthy to be paid attention to.FPSO have been widely used for the development of offshore oil and gas fields because of their attractive features which makes the transition and installation easier. However, FPSO are sited at specific locations so their structures have some features which are quite different from those general tanks. Such as increased duration of expo sure at sea; increased exposure to storms; increased difficulty in inspection and maintenance more effective protection from corrosion and fatigue design based on safe life approach and so on. For these reasons, compared with the regular vessels the calculation of FPSO has its particularity, like more fatigue check areas and high requirement of fatigue life.The procedure of fatigue analysis for FPSO is detailedly discussed in this paper based on the global FE model of FPSO and the results of whole structure analysis from general FEM program of ANSYS, which includes the determination of fatigue check area of FPSO, transient dynamic analysis and fatigue calculation method of main check position. The fatigue strength at the hot spots was evaluated according to ABS rules, and the computational results show that the structural dynamic analysis method and the S-N curves fatigue analysis method were suitable for fatigue analysis of FPSO, they were totally feasible. This is a new methodology of FPSO fatigue analysis with high utility value, and it has great meaning for the following research of FPSO fatigue analysis.