Quasi-dynamic global strength analysis of a passenger ship in regular waves

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Insinööritieteiden korkeakoulu | Master's thesis
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Master's Programme in Mechanical Engineering (MEC)
The current boom in cruise and passenger ship markets has led to a corresponding increase in the size of ships and their structural complexity. However, the optimization of capital expenditure costs remains a critical part in the design and construction of such ships. Additionally, the designers have at their disposal state-of-the-art tools and rational design methods for design and structural strength assessment of ships to ensure sufficient functional safety margins, especially for ships with general particulars and structural features that are not covered by the existing empirical Classification Rules. This master's thesis presents a rational quasi-dynamic response approach for the evaluation of global loads of passenger vessels. A rational quasi-dynamic response method couples wave-induced hydrodynamic pressures with a rigid hull idealization performed with ANSYS AQWA and ANSYS SpaceClaim. The CAD structural model of a typical cruise ship was produced using CADMATIC Hull with basic design accuracy. Furthermore, it was sufficiently optimized in ANSYS SpaceClaim to obtain an FEA model comprising of shell elements representing the primary and secondary parts of the structure. NAPA software was used for evaluating the still water bending moment. Consequently, the 3D diffraction/radiation panel code ANSYS AQWA was used to define the wave pressures acting on the hull and loads were mapped on the hull surface and transferred to the ANSYS FEM solver for hydro-structure coupling. As a result, still water and wave bending moments are received as well as the ship’s response. Comparisons against Class Society Rule wave bending moment amidships demonstrates that the direct evaluation of the wave bending moment and shear force envelopes along the hull girder may be a preferred rational approach in terms of assuring global structural strength and optimizing total steel weight. The outcomes of the thesis were presented during the Baltic Seas International Maritime Conference on 24.09.2019
Hirdaris, Spyros
Thesis advisor
Jokinen, Markus
passenger ship, global strength, FEM, quasi-dynamic, ship design
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