| Fatigue problem of local structure is likely to occur as deep-water semi-submersible platform is always under alternating wave load;it is very important to take fatigue assessment at the design stage.Spectral-based fatigue analysis method is a general solution for fatigue assessment of offshore platform,it's the most accurate fatigue analysis method now;but it desires much labor and time for its preprocessing,post-processing and data computing.Simplified fatigue assessment is a simple and quick way to filtrate fatigue strength at initial stage of structure design;but it has rare application on semi-submersible platform at present because of the difficulties to calculate Weibull distribution parameters and find dangerous wave cases.Key shills are summarized and spectral-based fatigue analysis is carried out for typical hotspots of a semi-submersible platform.Long-term Weibull distribution parameters of fatigue hotspots stress are estimated and dangerous wave cases are found,so that simplified fatigue assessment can be applied on semi-submersible platform.The main study work of this paper is as follows.1.The principle and application of fatigue assessment for semi-submersible platform is summarized;procedures of global strength analysis,spectral-based analysis and simplified fatigue assessment are introduced.2.Calculation models are established;dangerous fatigue hotspots are filtrated based on global strength analysis.Spectral-based analysis is carried out and fatigue life is calculated using SESAM program.3.Long-term distribution of typical hotspots stress is studied,parameters of Weibull distribution are estimated,and its accuracy and influencing factors are analyzed.4.The way to find dangerous wave cases is discussed,some critical wave cases is appended for long-term forecast of design wave,so that hotspots stress range can be calculated and simplified fatigue assessment can be taken out. |
PDF Full Text Request