Recently, various types of large-scale offshore structures, such as floating offshore airport, offshore floating bridges, floating offshore mobile base, floating offshore cities/plants, multiply connected floating breakwaters and wave energy converters, have been proposed. When designing such large-scale flexural floating structures, a complete coupled hydro-elastic theory including the structures' essential elastic modes needs to be developed; for instance, more complete diffraction/radiation/hydrostatic/inertia-analysis computer program including all the essential elastic modes has to be used for more reliable dynamic analysis. Such a hydro-elastic theory and computer program have been developed in the frequency domain. The fully coupled interactions among elastic motions, 6 DOF (degree of freedom) rigid-body motions, and diffracted and radiated waves are solved and the corresponding RAOs (response amplitude operators) are obtained. Subsequently, the full distributions of shear forces and bending moments are calculated considering the balance of inertia/restoring loadings and hydrodynamic loadings. The developed computer program is applied to a barge-type VLFS (very large floating structure) with various bending stiffness EIs. The contributions of constituent components for 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.
The world's increasing economy and population demand larger-scale food production, extended harbor and transportation system, and more mineral/energy extraction from the ocean. These demands require larger and more complicated structures. An example is the MegaFloat (1000 × 60 (120) × 3 meters) a close-to-prototype floating airport constructed in Tokyo Bay. US Navy also conducted MOB (mobile offshore base) project, which includes the development of naval offshore airport in the open sea by the connection of many identical floating units. Other examples of future marine structures, for which hydro-elasticity is important, are FOWT (floating offshore wind turbine) or WEC (wave-energy converters). Many of them are to be quite flexible and elastic.