The Ultimate Strength Analysis Of The Ship Structures Based On NFEM

The unstiffened plates and the grillage are the main structural type of ship, the ultimate strength of which and the ultimate bending moment of the ship hull girder are the main index for the evaluation of the ultimate strength of ship structures. Based on the nonlinear finite element method, the ultimate strength of the unstiffened plates, the grillage, the box girder and the ship hull girder are studied in the paper. Then a method for the prediction of the ultimate strength of the ship structure is established. The contents of this paper are as follows:1) The origin of the nonlinearity is introduced. And two methods of NFEM for evaluation of ship structure, the static method and the quasi-static method, are compared.2) The origin of the initial defect of ship structures is introduced, and then the method based on NFEM for the calculation of the initial defect of ship structures is established.3) A complete method of predicting the ultimate strength of unstiffened plates and grillage with NFEM is established, and the NFEM results are compared with the theoretical ones for the validation of the method. At the same time the influence of local load on the ultimate strength is discussed.4) A complete method of predicting the ultimate bending moment of the ship hull girder is established. And the NFEM results are compared with theoretical ones for the validation of the method. At the same time the influence of the initial defect on the ultimate bending moment of the ship hull girder is discussed.