Wave loading on floating docks under tow

Article type: Research Article

Authors: Ractliffe, A.T. | Mitchell, G.H.G.

Affiliations: University of Newcastle upon Tyne, U.K.

Abstract: A floating dock consists essentially of a flat rectangular base stabilised in the submerged condition by means of a vertical wall each side. It has the virtue of being towable from one port to another but during such a voyage is subject to waves imposing longitudinal bending, shear and torsion. These loads may be the largest encountered during the life of the structure and are therefore significant for its design. The only information previously available on this topic was based on simplistic quasi-static theoretical models which do not account for either the water surging over the floor of the dock, or the hydrodynamic forces resulting from pitch and heave. This paper describes a series of model experiments on a floating dock of representative proportions which is split in half transversely and fitted with straingauged straps measuring bending moment shear and torsion. The effects of draft, wave height, wave period and wave heading are investigated systematically and the results presented as families of non-dimensionalised curves. The effect of blocking the ends to prevent water surging through is also examined. The experimental bending moments are shown to be significantly lower than those obtained by quasi-static methods of analysis and non-linearities associated with free surface effects are found to be small enough to allow the use of a simple design formula.

DOI: 10.3233/ISP-1984-3135602

Journal: International Shipbuilding Progress, vol. 31, no. 356, pp. 88-93, 1984