| This work is financed by the National Natural Science Foundation of China. It belongs to No6.4 subproject: ptimum design of structural systems for offshore platforms of major project of the National Natural Science Foundation: ey Scientific Problem and Design Theory for Large-Complex Structures The theory and method of structure fuzzy optimum design for offshore platforms and some relevant problems are studied mainly based on the theories of structural fuzzy reliability, structural fuzzy optimization and engineering fuzzy set, and considering comprehensively the characters of optimum design for offshore platforms. The major contents in this thesis are summarized as follows: 1. The theory of method of fuzzy optimum lectotype for offshore platform The article puts forward a fuzzy optimization theory for multi-objective dynamic programming, based on these methods: AMP method, prior relation method, fuzzy gravity center method and the non-structural fuzzy decision theory. This model not only settles the problem of to measure the qualitative factors, but also establish the huge system of fuzzy dynamic programming, based on the AMP and prior relation. Considering various 13 factors of optimization objects and 8 projects, the method has been successfully used to testify by an offshore platform, and very ideal results have been obtained. Based the center platform. Multi-object fuzzy optimization is used to appraise platforms lectotype. The multi-level fuzzy optimization model is remarkable. 2. The research of the fuzzy optimization of structure and shape The model of structural fuzzy optimum design of offshore jacket platforms is established considering the fuzziness of constrained condition boundary. Design variables, object function and constrained conditions in the fuzzy optimum mode are considered with fuzzy method. According to the characteristics of offshore jacket platforms, the tolerance coefficient of the constrained condition boundary is determined with fuzzy optimization method. The optimum design for jacket platforms considering fuzzy fiictors is feasible and scientific. This paper presents a structure Fuzzy Topologic Shape Optimum Model of offshore jacket platform under multi-design rules and multi-constrained conditions. The design variables of the coordinates for nodes, which represent the pile embedded depth and the height of jacket floor, are adopted, and the FTSOM offshore jacket platform is established. The sequential two-level optimum algorithm is presented based on the design variable gradation. On the base of the finite element method, the sensitivity of the objective function and the node displacement is analyzed. By FTSOM, the value of object function is obviously lower than that of the initial design and the cross-sectional optimization. 3. The analysis and optimization of fuzzy reliability for jacket platform The research bases on the three major sides: stochastic mechanics of engineering, reliability analysis and the design method of reliability. The paper establishes the stochastic element method and the reliability optimal model. The paper calculates the reliability of platform based on the stochastic element. Author considers the uncertaint factors, introduces the stochastic element to calculate the plafform reliability, gains the more exact reliability. This paper researches the optimum reliability assignation, under based on the fuzzy factors, the reliability is assigne...
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