Full Life Cycle Of The Ship Security Assessment

When analyzing the structural strength of ship and offshore structure, the relevant parameters are given fixed values in the traditional method. And the maritime disasters are always handled by afterward research, neglecting the beforehand risk analysis. In fact, great tragedies still happen now and then, and many parameters obey some kinds of probability distribution. Some of them change with the lapse of time. Therefore, it is more reasonable to use a probabilistic and dynamic risk analysis method.According to this, this thesis focuses on a FPSO's intact/damaged longitudinal strength disabled model during its lifetime, by using the Formal Safety Assessment(FSA). The load, ultimate strength, reliability analysis and FSA are considered together in order to forecast risks and collect practical data.Aiming at these purposes, firstly, this thesis suggests several damaged conditions and calculates the still water loads of intact/damaged condition. Secondly, the wave loads are calculated, too. Thirdly, the intact ultimate bending moments which are influenced by corrosion and decline yearly and the damaged ultimate bending moments which are influenced by corrosion and structural damage are calculated by program of ISUM. All these data's distributions are given at the same time. By using the above data, the reliability analysis is carried on with the AFOSM and JC method. After getting the reliability indexes, the probabilities of failure can be obtained. Finally, the probabilities of failure are taken as evaluation indexes to carry through the FSA. It can be seen from the result that the changes of ultimate strength and probability of failure which are only caused by corrosion are not shrewd. But the structural damage has great effect on reliability and will lead to severe sequence if it happens. So it should be regarded highly. Further more, the thesis gives different blue prints which are against the situations of too high probabilities of failure, and the prints are compared in order to give the suggestion of decision during the phase of FSA.This thesis combines the FSA with reliability analysis and applies them on the FPSO. It gives out the realization process of practicing the theories and gets valuable data and conclusions which will benefit the future similar work. At the same time, it will be helpful to make risk-based criterion and evaluate other kinds of ship in the future. It makes for improving the safety level of the maritime industry.