Systematic Analysis on Mooring Systems of Large Scale Hoating Structures

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As candidates of moorimg systems for large scale floating structures, five kinds of systems such as Dolphine/Jacket-Fender Mooring, Catenary Mooring, CALM,SALM and Tension-Leg Mooring were selected. The anlytical models for analyzing relations between mooring force and displacement in these mooring systems were surveyed. Based on the survey results, following simulation programs were developed : analytical theory for Catenary, application of catenary theory for CALM,numerical intrgration method for SALM,static characteristics analysis for Tension Leg and static matrix method for Dolphine/Jacket-Fender.In addition, the existing data of mooring systems were surveyed on installation depth, dimensions of mooring srtuctures, materials and so on. These data were used as input data to the analytical method developed and relations between mooring force and displacement were calculated. The results of these calculations were illustrated as figures showing water-depth vs. mooring force relation corresponding to given horizontal displacement. These figures are convenient to select appropriate mooring system corresponding to the magnitude of mooring force when horizontal allowable displacement and expected water-depth are given. On the other hand, enlargement of applicable range in the water-depth vs. mooring force relation was tried by analyzing and enlarging rationally surveyed data of each mooring system. As a result of this trial, tension leg still has possibility with respect to water-depth and mooring force. Considering this result with future mooring characteristic requirement, it is concluded that inclined tension leg will be prospective. Therefore, a large scale semisubmersible type of model was tested by regular head-sea waves and displacements, strains and fluctuated tension of legs were measured. The characteristics of inclined tension leg were analyzed and desing philosophy in floating structures moored by inclined tension legs was discussed.