Longitudinal Strength of Ships: A Simplified Approach

Gordo, Jose Manuel Antunes Mendes (1993) Longitudinal Strength of Ships: A Simplified Approach. MSc(R) thesis, University of Glasgow.

Abstract

A simplified method is proposed to predict the behaviour of full cross-sections of ships under longitudinal bending. The method assumes that plane sections remain plane and thus a linear distribution of strains is considered over the cross-section. The hull girder collapse strength may be calculated for any heeling conditions. The large panels between the primary framing system of the cross-section are assumed to have the same behaviour as their significant individual elements - stiffener with associated plate. The load-shortening curves of the stiffened plates is assessed using the Jonhson-Ostenfeld or the Perry-Robertson formulation. These formulations are basically used to determine the flexural collapse strength of the stiffened elements, but here, they are extended to cover the whole range of strains, predicting the pre and post buckling behaviour. The reduction of the effective width of the associated plate during the path loading is accounted for by considering approximated average stress- strain curves of the plate elements and the Faulkner proposal is adopted to quantify the impact of this reduction on the load-shortening curve of the column. The effects of flexural-torsional buckling are considered, applying the methods developed by Adamchak and Faulkner, both in respect to the ultimate carrying capacity of the stiffened plate and the post buckling behaviour. The stress-strain curves of the plate elements are determined in relation to a design formula of the ultimate strength of simply supported plates and the concept is extended in order to obtain the curve for the whole range of strains. The method includes the effect of residual stresses in the plate elements by modifying the material properties. So the impact of plate residual stresses on hull girder strength may be investigated. Also available is a method to incorporate the effect of plate and stiffener distortions and their effects on the ultimate strength of the ships. An investigation of the effect of secondary load systems in plate elements is made. Formulae to include the effect of biaxial loading, lateral pressure and edge shear are indicated based on a study of the ultimate strength of plate elements. Concerning to the ultimate bending moment of the hull girder, the effect of residual stresses and stiffener distortions is investigated as well as the consequences of corrosion and the use of high tensile steel. The strength of the hull girder is calculated for any angle of heel by a method that ensures a constant angle between the position of the neutral axis at any curvature and the horizontal.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Additional Information: Adviser: Douglas Faulkner
• Keywords: Naval engineering
• Date of Award: 1993
• Depositing User: Enlighten Team
• Unique ID: glathesis:1993-75462
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 20:02
• Last Modified: 19 Nov 2019 20:02
• URI: https://theses.gla.ac.uk/id/eprint/75462