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A General Formula for Calculating the Value of Transverse Moment of Inertia by Observing the Roll Motion of Ships
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 Title & Authors
A General Formula for Calculating the Value of Transverse Moment of Inertia by Observing the Roll Motion of Ships
Choi, Soon-Man;
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The transverse moment of inertia is an indispensable factor in analyzing the roll motion characteristics of ships and the calculating method needs to be based on the more reasonable theories when deciding the value as the results and reliability of analysis could be much affected by the correctness. However, the mass distribution and shape of hulls are quite complicated and give much difficulties in case of calculating the value directly from the ship design data, furthermore even acquiring the detailed design data for calculation is almost impossible. Therefore some simpler ways are practically adopted in the assumption that the gyradius of roll moment can be decided by a given ratio and hull width. It is well known that the responses of the free roll decay are varied according to the value of roll moment in view of roll period and amplitude decay ratio, so that the general formula to get the moment value can be derived also from the observation of roll decay responses. This study presents how the roll period and decay ratio are interrelated each other from the roll motion characteristics with suggesting a general formula to be able to calculate roll moment from it. Finally, the obtained general formula has been applied to a ship data to check the resultant characteristics through analyzing graphs and showed that the roll moment becomes more accurate when rolling period and decay ratio are considered together in calculation.
Ship motion;Rolling decay;Roll gyradius;Transverse moment of inertia;Rolling damping coefficient;Roll amplitude decay ratio;
 Cited by
IMO Resolution A.749(1993), Code on Intact for all Type of Ships Covered by IMO instruments.

Kruger, S. and F. Kluwe(2008), A Simplified Method for the Estimation of the Natural Roll Frequency of Ships in Heavy Weather, HANSA Bd 145, pp. 1-7.

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Surendran, S. and J. Venkata Ramana Reddy(2003), Numerical simulation of ship stability for dynamic environment, Ocean Engineering, Vol. 30, No. 10, pp. 1315-1317.

Vredeveldt, A. W. and J. M. J. Journee(1991), Roll motions of ships due to sudden water ingress, calculations and experiments, International Conference on Ro-Ro Safety and Vulnerability the Way Ahead, RINA, Vol. I, pp. 13-30.