Local Plastic Failure Analysis For The Deck Structure Of Semi-submersible Platform

As a typical marine engineering structure,Semi-submersible offshore platform has been on the concern of the majority of marine engineering scholars. Due to inaccurate operation of crane and other equipments the dropping incidents usually occurred on the platform deck.Dropping accidents ranked top one in the offshore platform accident. In occasional extreme sea conditions, some local structures, such as the moon pool corner often have plastic failures problems, which caused huge losses to the production and personal property. In this paper, local plastic failure problem of the deck structure of semi-submersible platforms was studied, with focus attention on the plastic failure problem of the deck structure subjected to the crash of dropped objects and the plastic failure problem of the moon pool corner under typical loads of the semi-submersible platforms. The major work of this paper is listed as followings.1. Some non-linear elastic-plastic problems are studied to get a basic understanding of content and process of elastic-plastic research and nonlinear finite element analysis theory.To explore the finite element modeling techniques which is applied to the falling objects problems, the finite element analysis parameter are set reasonably referring to the test results of the literature.2. The plastic failure problem of semi-submersible platform which is subjected to the crash of falling objects is studied in this paper. The effects of different forms of falling objects as well as the collision parameters on results are investigated and formula is fitted by the results of numerical simulation analysis, which guides the actual engineering projects.Guidance and advice on the plastic failure analysis of structure under the crash of falling objects are put forward and a certain degree of complementary to criterion is given in the end.3. After clarifying the distinction and relation between plastic analysis and ultimate strength analysis, the plastic failure analysis method and analysis technique of the moon pool corner are explored. In the process of analyzing the plastic failure problem of moon pool corner of semi-submersible platform, reasonable loading and boundary conditions are set according to typical load cases of semi-submersible platforms. Meanwhile, the components which are prone to plastic failure under different kinds of loading mode and the cases on which additional attention should be paid are clear. The plastic failure process of moon pool corner is also traced, observed and analyzed. A certain degree of complementary to criterion is given at last.