In this paper, influences of design strength on natural modes of floating structures are examined by analyzing natural frequencies and mode shapes of floating bodies with nonuniform stiffness. A FSRU (Floating Storage and Regasification Unit) is considered as an example structure. Natural modes such as natural frequencies and modes shapes are calculated by the subspace iteration method which is widely used as a solver of eigenvalue problem. Various numerical models of FSRU are considered. One is a simplified model of which stiffness is uniformly distributed. The other is a model with stepped distribution of stiffness. The third model has a triangular stiffness distribution. By comparing the results of each model, the influences of nonuniform strength distribution on natural modes are investigated.
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