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Some aspects of geometric stiffness modelling in the hydroelastic analysis of ship structures

Hydroelastic analysis of ship structures is a complex task of determining the interaction between the structure motion and vibrations on the one hand and water on the other. In the governing equation of motion, the unified restoring and geometric stiffness play an important role. The hydroelastic problem is solved by the mode superposition method based on the finite element technique. Simplified modal geometric stiffness is derived by neglecting the rotational degree of freedom in the shell finite elements. The influence of such a simplification on accuracy is analysed in the case of beam flexural vibrations, where distributed mass is also modelled by a set of lumped masses. Based on good results obtained by both the direct calculation and some commercial software packages, the same approach is used for beam buckling analysis. The performed analysis shows that the use of a simplified geometric stiffness matrix yields quite good results and its application in the hydroelastic analysis of ship structures is acceptable.

Structural analysis ; FEM ; Beam model ; Natural vibrations ; Buckling

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