| After more than half a century of development,the semi-submersible platform has been currently in its sixth generation,and its design and development for the seventh generation has also been on the agenda.It was found that in the early stage of platform design,the conventional platform structure evaluation method and operation process would consume a lot of labor and time.The existing structural strength analysis is based on the three-dimensional finite element model which is represented by the plate and beam element.It causes a large amount of calculation and lots of analysis categories for the hundreds of thousands of units calculation and processing in three aspects of yield,buckling and fatigue.The completion of an overall strength assessment often takes several weeks or even a month.In the stage of ship development,the design of platform and the strength evaluation of structure alternate with each other,the time of analysis and computation are multiplied.Therefore under the premise of ensuring a certain precision,it has practical implications to research fast assessment methods and use simplified methods appropriately to improve the efficiency of the analysis of the structure.This content is mainly aimed at the shortcomings of the conventional evaluation methods such as large amount of calculation,too much time and so on,to research fast assessment methods which is suitable for the semi-submersible platform.According to the analysis of the existing the technology of strength assessment,the orthogonal simplified method for the stiffened plate is put forward in this paper.Aiming at the key problems of structural equivalent in rapid assessment method and based on the theory of anisotropic plate and composite section beams in structural mechanics system,taking theoretical derivation for the equivalent parameter,the problem about equivalent conversion is solved in this paper in aspects of the spacing,direction,material,shape and size of stiffener.In the course of the research,this paper adopts the contrast strategy and selects the representative ultra-deep-water platform design case,and then take the conventional evaluation method,the method of bone area equivalent,simple rigid frame simplification method and orthotropic plate simplification method,after that assess the operation in the same design premise and similar personnel technical level conditions,finally compare the efficiency and accuracy of the fast method.The analysis process is as follows:Firstly,based on the design wave analysis and the stochastic analysis of DNV,the design wave is selected and the load calculation of the platform is completed.Then the finite element modeling of the platform is completed and various of characteristics loads are applied to finish the strength analysis calculation according to the conventional method and the above simplified methods.Lastly,for the main node and the position of platform column,buoy and transverse bracing,the data of structure response processing,evaluation and comparison of strength are completed.In addition,in this paper,the conventional method is compared with the simplified methods on the number of units,the calculation time and the accuracy of the results.The results show that compared with other simplified methods,the equivalent method of orthotropic plates and the conversion method of aggregate area have higher accuracy and the stiffeners are eliminated.The density of plate element is reduced and the efficiency is improved significantly. |
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