RECENT DEVELOPMENTS IN THE THEORY OF SHIP VIBRATION
1953
McGoldrick, R. T. | Gleyzal, A. N. | Hess, R. L. | Hess, Jr, G. K.
It is shown in this report that by considering the ship hull as a floating beam having shearing and bending flexibility with a distributed viscous damping proportional to mass it is possible to derive equations of motion under external forces by the general Rayleigh method which yields a solution in terms of normal modes of motion. Practical methods of determining natural frequencies and normal modes are discussed, and it is shown that solutions based on finite- difference equations can be obtained with the use either of a digital sequence calculator or an electrical analog. A discussion is given of coupled horizontal bending and torsional modes as well as vertical modes of vibration. It is pointed out that the finite-difference-equation method applied to vertical vibration of a vessel of merchant type has given results in good agreement with experimental values up to the sixth vertical mode.
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