Total System of Analysis on the Longitudinal Strength of Ships

Abstract

In this paper, an outline is presented of the total system of computer programme that has been developed by Nippon Kaiji Kyokai for the rational and direct evaluation on the longitudinal strength of hull girder of oceangoing vessels.This system is consist of an integrated group of individual programmes which include an input data processing and automatic generating programme as well as those concerned with the theoretical analysis on the oscillating motion of ships among waves with use of strip method, structural analysis and stress calculations of hull girders based upon the general bending and torsion theory of thin walled beams, and the statistical analysis on the fluctuating stresses in longitudinal members of the ship. The out put of the computations gives a direct information on the probability of exceeding a certain prescribed value of the stresses caused in the longitudinal members during the whole life time of the ship.Then, a discussion is made into the detail of a series of calculations which are performed on the longitudinal strength of existing oil tankers, of which the deadweight capacity varies from 50, 000 to 500, 000 tons. It is found from this analysis, that the fluctuating stresses in the longitudinal strength members due to vertical bending of hull girders are almost in the same level among these ships, whereas those due to horizontal bending of the hull girders show a gradual rise with increase of the size of the ships.