Theoretical Calculation of Lateral Shear Force, Lateral Bending Moment, and Torsional Moment Acting on the Ship Hull among Waves

Abstract

This paper deals with a method of the theoretical calculation of the lateral wave loads (i. e. shear force, bending moment, and torsional moment) acting on ship's hull in oblique regular waves.The strip theory utilizing the hydrodynamic coefficient obtained by Tasai's theory is applied to this method, and a correction is made on the viscous roll-damping coefficient.In the calculation of torsional moment, the effect of shear center height is considered.The longitudinal distributions of lateral wave loads exerting on a typical ship model are shown herein. Then comparisons are made between the calculated values and the data of experiments carried out at several model basins.The calculated and measured values of the lateral wave loads-especially, of the lateral shear force and lateral bending moment-are in good agreement with each other. However, the calculated values of the torsional moment are, in some cases, slightly different from the measured values.This calculation method seems to be practical in predicting the lateral wave loads as a preliminary design stage routine, though it is necessary to obtain more accurate evaluation of distribution of roll-damping moment and transverse moment of inertia along the ship's longitudinal axis.