Comparative study of full length and two cargo holds 3D models for strength analysis of a tanker ship structure

Abstract

This study is focused on the sensitivity analysis of different structural models used for global and local strength assessment in the case of head equivalent design wave loads acting on the ship hull. Four type of structural models are considered: a 3D-FEM model full extended over the whole ship length, one sided, with coarse mesh shell elements; a 1D equivalent beam model, vertical bending and shearing behaviour, with the mass distribution and the external hull shape imported from the 3D-FEM model, with a coarse beam mesh; a 3D-FEM model extended over two cargo holds amidships, in two versions with coarse and fine mesh shell elements for structural details, with model characteristics and loads taken directly from the 3D-FEM extended model and the boundary displacements and rotations from the elastic 1D-equivalent beam model. In the case of 3D-FEM full extended model, the balance ship-EDW is obtained by user subroutines implemented directly in the FEM program. For 1D model an own program code is used in the case of head EDW waves, with a non-linear iterative approach. The stress post-processing of the 3D-FEM models is done by specific user subroutines. As numerical study case a chemical tanker with 3950.6 m3 cargo capacity is considered. The study by the four structural models has revealed a good correlation of the numerical results, corresponding to the specific sensitivity ensured by each model