Hydroelastic Analysis and Statistical Assessment of Flexible Offshore Platforms
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by The International Society of Offshore and Polar Engineers. Recently, various types of flexible offshore structures, such as floating offshore airports and bridges, multiple connected floating breakwaters, and wind/wave energy converters, have been proposed. When designing such large-scale flexural floating structures, a complete coupled hydroelastic theory, including the floating structures deformation and their interactions, needs to be developed; that is, a more complete diffraction/radiation/hydrostatic/inertia-analysis tool, including all the essential elastic modes, has to be used for more reliable dynamic analysis. Such a hydroelastic theory and the numerical tool have been developed in the frequency domain. The developed numerical analysis is applied to a barge-type floating elastic body with various bending stiffness after convergence tests against the number of high-order elements and elastic modes. Fully-coupled interactions among elastic motions, 6-DOF (degree of freedom) rigid-body motions, and diffracted and radiated waves are solved for a wide range of wave frequencies and the corresponding RAOs (response amplitude operators) are achieved. The elastic-mode RAOs are compared against those obtained from an independently developed time-domain program for verification purposes. Subsequently, distributions of shear forces and bending moments are achieved on the basis of the balance of inertia, restoring loadings, and hydrodynamic loadings. The stress resultants are also verified against the independently developed time-domain program and a plate theory-based calculation. The contributions of constituent components for the shear forces and bending moments are also compared. By using the frequency-domain results, how to estimate the statistical maximum shear force and bending moment along the sections of the barge in irregular waves is explained by two different approaches. In both dynamic and structural analyses, the resonance phenomena for elastic modes are investigated and discussed.
