Motion Characteristics of Floating Structures

by Akira Nishitani, Post Doctoral Research Assoc.; Dept. of Civ. Engrg. and Engrg. Mechanics, Columbia Univ., New York, N.Y. 10027,
Masanobu Shinozuka, (M.ASCE), Renwick Prof. of Civ. Engrg.; Dept. of Civ. Engrg. and Engrg. Mechanics, Columbia Univ., New York, N.Y. 10027,

Serial Information: Journal of the Engineering Mechanics Division, 1982, Vol. 108, Issue 6, Pg. 1277-1296

Document Type: Journal Paper


An engineering approach to the time domain analysis which accounts for the effects of damping is developed for the purpose of evaluating the rigid body response motion of a two-dimensional floating body confined in a fixed basin. The frequency dependent added mass coefficients are first obtained under the assumption of an ideal fluid. Then the equations of motion in the frequency domain are constructed by artificially introducing the damping coefficients. Frequency response functions then follow logically from these equations of motion and are inverse-Fourier transformed to produce the impulse response functions. Essentially, three forms of damping coefficients are considered and experiments are then performed to determine how well these forms reproduce the experimental results. The optimum values of the damping ratios are also estimated from the experiments and their use for the analysis of large scale floating bodies is suggested. Finally, the causality conditions are verified numerically and it is found that they are satisfied at acceptable levels of engineering accuracy.

Subject Headings: Damping | Equations of motion | Two-dimensional analysis | Rigid body dynamics | Motion (dynamics) | Basins | Verification | Numerical analysis

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