Hydro-structural issues in the design of ultra large container ships

Abstract

The structural design of the ships includes two main issues which should be checked carefully, namely the extreme structural response (yielding & buckling) and the fatigue structural response. Even if the corresponding failure modes are fundamentally different, the overall methodologies for their evaluation have many common points. Both issues require application of two main steps: deterministic calculations of hydro-structure interactions for given operating conditions on one side and the statistical post-processing in order to take into account the lifetime operational profile, on the other side. In the case of ultra large ships such as the container ships and in addition to the classical quasi-static type of structural responses the hydroelastic structural response becomes important. This is due to several reasons among which the following are the most important: the increase of the flexibility due to their large dimensions (Lpp close to 400 m) which leads to the lower structural natural frequencies, very large operational speed (> 20 knots) and large bow flare (increased slamming loads). The correct modeling of the hydroelastic ship structural response, and its inclusion into the overall design procedure, is significantly more complex than the evaluation of the quasi static structural response. The present paper gives an overview of the different tools and methods which are used in nowadays practice.

Buoyancy coupling with structural deformation analysis of ship based on finite element method

“…Hydroelasticity takes the hull structure and fluid as a whole system, the dynamic pressure of fluid is the external load of hull structure, and the magnitude of dynamic pressure depends on the displacement, velocity and acceleration of hull structural vibration. The hydroelasticity methods include frequency domain analysis (Senjanović et al, 2014a(Senjanović et al, , 2014bMalenica and Derbanne, 2014) and time domain analysis (Kim et al, 2013), and they are applied to ships with a natural vibration frequency close to the wave encounter frequency, such as container ship (Kim et al, 2013;Senjanović et al, 2014aSenjanović et al, , 2014bMalenica and Derbanne, 2014), and very large floating structure (Cheng et al, 2015) etc.…”

“…Another method is to calculate the fluid pressure based on 3D hydrodynamic model, based on which both hydrostatic load and hydrodynamic load could be solved. Malenica and Derbanne (2014) use a linear quasi static hydro structure interaction model to analyze structural responses. In Malenica's method, the hydrodynamic and hydrostatic load are calculated by 3D hydrodynamic model, and translated into the FE model on the premise of perfect equilibrium.…”

Quasi-Static Response of a 19,000 TEU Class Ultra Large Container Ship with a Novel Mobile Deckhouse for Maximizing Cargo Capacity

“…Reference is made to the newly introduced BV Rule Note NR 583 [13] and to the paper of Malenica and Derbanne [3]. In these documents, the basic assumptions on the numerical methods and the corresponding methodologies are described and are strictly applied in this study.…”

“…Special attention should be paid to this issue and the way in which this was done in the hydro-structure tool HOMER is described in [3]. Meanwhile, in order to evaluate the local stress concentration in the particular structural detail, the so called top-down analysis should be used [19].…”

“…A specific characteristic of Ultra Large Container Ships (ULCS), compared with the other ship types, is that they are more likely to experience the hydroelastic type of structural responses called springing and whipping [1], [2], [3], [4], [5], [6], [7]. That is caused by their large dimensions leading to higher structure flexibility, a relatively high service speed, and large bow flare.…”