The importance of mathematical models for ship hydroelastic analysis grows with the design of ever larger container ships which have specific design and exploitation characteristics. Compared with other merchant ships, they are characterized by relatively lower torsional stiffness, which in combination with encounter sea states related to their higher speed of approximately 27 knots can cause resonance effects. This paper is based on research activities and results of the EU FP7 project Tools for Ultra Large Container Ships (TULCS), with particular emphasis to the part which deals with global hydroelastic loading and response. Special attention is paid to beam structural model based on the advanced beam theory. It includes shear influence on both bending and torsion, contribution of transverse bulkheads to hull stiffness as well as an appropriate modelling procedure of relatively short engine room structure. Finally, ship hydroelastic response assessed by sophisticated beam model is compared with the results of fully coupled 3D FEM + 3D BEM hydroelastic analysis. The obtained transfer functions of sectional forces confirm that the developed model is very useful numerical tool for the designer and represents a reasonable choice for determining wave load effects on ULCS, in early design stage.
The structural design of Ultra Large Container Ships (ULCS) is driven by the economies of scale of transporting large numbers of containers in one ship and the commercial pressing of reducing the total production cost and steel weight through optimisation. Due to increase in size, the natural frequencies of the hull girder can fall within the range of wave load excitation forces. At the same time, due to operational requirements, the cruising speed of UCLS is relatively high increasing the encounter frequency significantly. Several important issues affecting ULCS have been identified: nonlinear quasi-static hydrodynamic loading, springing, slamming, green water and whipping.
