engleski

Assessment of stress concentrations in large container ships using beam hydroelastic model

The increase in world trade has largely contributed to the expansion of sea traffic. As a result, the market demand is leading to Ultra Large Container Ships (ULCS), with expected capacity up to 18000 TEU and length about 400 m, without changes of the operational requirements (speed around 27 knots). The particular structural design of the container ships, leads to open midship sections, resulting in increased sensitivity to torsional and horizontal bending loads which is much more complex to simulate numerically. At the same time, due to their large dimensions, the structural natural frequencies of ULCS become significantly lower so that the global hydroelastic structural responses (springing & whipping) can become a critical issue in the ship design and should be properly modelled by the simulation tools since the present Classification Rules don’t cover described operating stages completely. The methodology of hydroelastic analysis includes the definition of the structural model, ship and cargo mass distributions, and geometrical model of ship surface. First, dry natural vibrations are calculated, and then modal hydrostatic stiffness, added mass, damping and wave load are determined. Finally, wet natural vibrations, as well as the transfer functions (RAO – response amplitude operator) for determining ship structural response to wave excitation, are obtained (Senjanović et al., 2008a, Tomašević, 2007). The hydroelastic problem can be solved at different levels of complexity and accuracy. The best, but highly time-consuming way is to consider 3D FEM structural model and 3D hydrodynamic model based on the radiation-diffraction theory. Such an approach is recommended only for the final strength analysis. However, in this paper the beam model is coupled with 3D hydrodynamic model....

Stress concentrations; Hydroelasticity; Beam model; Hydrodynamic model; Hydrostatic model; Fatigue; Container ships

Cjelovita verzija rada objavljena je u digitalnoj inačici zbornika (ISBN: 978-953-6986-06-4)