Strength analysis of ship structures with open decks

Structural strength calculation by finite element analysis (FEA) is increasingly important in design and approval process. In recently developed DNV GL guidelines, procedures for different types of FEA including global strength analysis, cargo hold analysis and fine mesh analysis are provided. These modern guidelines define appropriate loading, boundary conditions and mesh size for FEA to be used with acceptance criteria in the rules. Traditionally, cargo hold and global strength analysis in ship design were dealt with separate finite element (FE) models and analysis approaches. But using same mesh and load cases, the cargo hold FE model has to deliver identical results as the global FE model. The key success factors for suitability of results, particularly for open deck ships under torsion loads, are related to the correct application of boundary conditions on cargo hold FE model. Results from testing this approach for a bulk carrier and a container ship are reported.