Study On The Global Structural Strength And Hot Fatigue Strength Of The New Deep-water Octagonal FDPSO

With the depletion of onshore oil and gas resources,the world is actively exploring Marine resources,and the offshore platform gradually becomes an important strategic equipment.As new kind of deep water oli and gas equipment,Floating Drilling Production Storage and Offloading(FDPSO)have integration function of development and production,which based on the design of floating Production Storage and Offloading(FPSO)and semi-submersible platform,caught the attention of more and more companies.Under the worse sea states,the assessment of global strength and fatigue strength become more important when platform suffering the waved and cyclic load.Taking aimed FDPSO as calculation model,analysis hydrodynamic response,complete the global strength and fatigue strength of hot spot.In addtional,analysis procedures of global strength and fatigue strength are presented.First,introducing the structure of the main modules and distribution of the overall loading conditions and environment when platform in operating and survival conditions,combined with the SESAM software of DNV to complete hydrodynamic wet surface and mass model of target platform.The seven kinds of wave characteristic load conditions are based on recommendation of DNV and ABS and characteristics of Structural.Combined with three-dimensional potential flow theory and design wave of long-term response theory,completing the transfer function and long-term response of characteristic load to determine the design wave parameters.Secondly,using software of MSC.Patran to establish the structural coarse grid model.Based on the PCL programming,exerting wave load to FE model.The other design load through the establishment of MPC barycenter position or function of software.The FE analysis of the platform structure was completed by comparing the three boundary conditions.Based on four kinds of working condition of loading stress result to carry out stress concentration area selection and assessment of global strength.It is concluded that the selection principle and the global strength of the wave load condition of the platform feature and the area where fatigue damage may occur.Finally,introducing processes of spectral analysis method which is based on the S-N curve and Miner principle of cumulative damage.Combined with the high stress area to filter the hot spots and establish detailed grid model.The fatigue damage and life of eight hot spots were analyzed,and the position of fatigue damage is found in the brace connection and the inflection point of the pontoon and column.Introducing processes of deterministic analysis method which is based on the design wave.Combined with the theory and method of design wave in chapter 3,the damage and life of eight hot spots under seven control loads were calculated.It is concluded that the inflection point of the pontoon and the column connection is the most damaged under the oblique wave.Compared with the two methods,the results of spectral analysis method are accurate and the result of deterministic analysis method is conservative but the workload is small.