Aspects relevant for operational and structural design of a wide-breadth, neo-panmax containership were addressed. First, speed loss in waves was investigated. Second, wave-induced global hull girder torsion was determined to assess the effects of the increased breadth on this load component, generally considered critical for the ship’s structural strength. An extended Reynolds-averaged Navier–Stokes (RANS) equations solver simulated the ship advancing in calm water as well as in selected regular head and bow waves. A boundary element method (BEM) computed transfer functions of wave-induced ship response. Before using spectral techniques to obtain long-term predictions of hull girder torsion, these transfer functions were corrected to account for non-linear effects. To assess the reliability of the computed long-term hull girder torsion, the extended RANS equations solver was used to perform additional simulations for this ship advancing at selected speeds in equivalent regular design waves that represent wave conditions considered critical for structural design. Except for the very forward part of the ship, long-term BEM-based predictions of wave-induced hull girder torsion did not exceed rule values. Comparative BEM and RANS predictions of hull girder torsion differed significantly, underlining the need to validate the predictions systematically.

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Many modern ships, particularly large containerships, are characterized by extreme bow flare, large stern overhang, and low torsional rigidity due to an open deck structural configuration. Software package GL ShipLoad was developed as an aid to assess the structural integrity of such ships. This software tool became the standard method to generate rule based loads for a global strength finite element analysis of sea going displacement ships. It efficiently generates loads based on first principles. A graphical user interface facilitates the convenient application of ship and cargo masses to the finite element model and aids in the selection of relevant design wave situations. User defined selection criteria, such as maximum values of rule based bending moments, shear forces, or torsional moments, specify which waves have to be chosen for the global strength analysis. This approach yields a reduced number of balanced load cases that are sufficient to dimension the hull structure. To adequately simulate roll motion, additional roll angles are analyzed that simulate realistic distributions of torsional moments over the ship length. A strength analysis of a typical post-panamax containership demonstrated the load generation procedure. First, efficiently modeled mass items were grouped into reusable assembled masses for the ship at hydrostatic equilibrium. Second, regular design wave scenarios were estimated, and hydrodynamic pressures for a large number of regular waves were computed. Third, a reduced number of relevant wave situations were automatically selected, and balanced hydrostatic, hydrodynamic, and inertia loads were applied to the finite element model. Enforced roll angles were found to contribute significantly to the initial torsional moment in the fore holds. Finally, based on a locally refined FE submodel of the hatch corners in way of the ship’s fore hold, a fatigue analysis was performed to assess effects of critical loading under enforced roll angles.

A linear boundary-element method and a Reynolds-averaged Navier-Stokes (RANS) equations solver were combined to predict maximum green water loads on a typical cruise ship of medium size. For structural analysis, a one-way coupling mapped the hydrodynamic pressure from the finite-volume grid onto the computational structural dynamics finite element mesh. First, linear long-term maximum ship responses were determined by a boundary element method combined with long-term statistics based on spectral methods; transfer functions of these responses were used to define response-conditioned wave trains inducing the linear long-term maximum ship response. The investigated wave sequences were correlated to a dedicated probability level for a lifecycle time of 20 years in the North Atlantic environmental wave conditions and for a ship speed of six knots. Critical impact locations were found to include the weather deck in the foreship, the front wall of the superstructure and the overhanging bridge deck. Predicted loads were compared to experimental data obtained in conditioned wave trains and in extreme irregular sea states. Numerical and experimental results revealed significantly higher loads than design loads specified by classification society rules. Pressure peaks on the weather deck and the superstructure front wall were comparable to rule-based design pressures for breakwaters on containerships and exceeded pressure peaks on the bridge deck.