| Semi-submersible platform is one of the major equipments for petroleum and natural gas exploitation. It is necessary to evaluate the structure strength of the unit in order to ensure its security. The main ship classification societies and authoritative organizations in the world, such as ABS, DNV, API, promulgate rules and guides for strength assessment of offshore structures. However, the approach of evaluation except the basic principle is not illuminated in the issues. So the major purpose of this thesis is to provide a reasonable plan for the pivotal steeps in the analysis of structure strength and the following problems are emphatically investigated.1) Investigate the method of selecting design wave which would be used in strength assessment. Two ways that are the stochastic method and the deterministic method would be studied and compared in determining the parameter of design wave respectively.2) Determine the necessary load cases for strength analysis of platform in accordance with its typical operating conditions, specific structural types, the design limiting regular waves and so on.3) Establish the global structural FE model with spacial plate-beam combined elements and discuss the principle, method and notice of modeling in order to lay a good foundation for strength assessment.4) Introduce the principle and approach of yield and buckling strength for semi-submersible platform and provide logical resolving ways for some important elements in the strength evaluation process.5) Discuss the theory and method of fatigue strength assessment, check all the types of joints in the unit using direct computing method based on spectral analysis, and finally present the way of fatigue strength evaluation for aged platform.
|
PDF Full Text Request