This paper investigates the challenges and opportunities emerging from the application of finite element method-based open-source software in ship structural analysis. Application of general procedure for development and assessment of FEA software used for ship structures is presented and demonstrated on the new upgrade of open-source FEA software OOFEM (Object-Oriented Finite Element Method). Properties of new quadrilateral shell FEs implemented in OOFEM are presented. The new FEs comply with relevant class requirements and are suitable for the usage in the analysis of real-world ship structures. The implemented software upgrade is validated on a series of test problems ranging from simple engineering structures to a real-world model of one part of megayacht’s superstructure. The benefits of validation tests and challenges encountered in the process of selecting the tests and interpreting their results are also discussed.

The ultimate strength of the hull girder represents one of the key criteria in the design of large thin-walled steel structures such as ships and aircrafts. For large ship structures, the hull girder’s ultimate strength is expressed as the maximum internal vertical bending moment that the hull structure can absorb before collapse. In this paper, a progressive collapse analysis of the hull girder has been performed for several different variants of large steel thin-walled box girders, taken from the literature as benchmark cases, using the nonlinear finite element method (NLFEM), considering both material and geometrical nonlinearity. Results from the performed calculations were compared to the numerical results of other researchers published in the literature, as well as the results of our physical experiment. The influence of initial geometrical imperfection on the value of the ultimate bending moment achieved with NLFEM has been investigated.