Bending of Beams and Girders

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Chapter 4 introduces the application of the simple beam theory to ship structural members. The limitations of application of the simple beam theory to thin-walled asymmetrical sections are highlighted. A full explanation of the idealization of beam elements is illustrated. The various configurations of end supports commonly used in ship structure are given. The importance of determining the effective span of beams is stressed. The effective breadth concept is explained for uniform and curved structural members. The concept of modeling ship structure assemblies by beam elements is introduced. Several examples of 2D and 3D modeling of deck, bottom, side and bulkhead ship structure using beam and plate elements are illustrated. The various types of boundary end conditions commonly used in ship structure analysis are given. The concept of span points and effective span of a beam are clarified. A method is given to determine the optimum span length of a beam and the size of bracket to be fitted at both ends. The influence of the type of end support on the magnitude and distribution of the bending moment are presented. Bending stresses in beams constructed with high tensile steel. Flexural stresses in symmetrical sections, sections with one axis of symmetry and is explained fabricated asymmetrical sections are presented. The importance of calculating the equivalent stress is highlighted. A simple procedure for calculating flexural warping stresses is given. The main parameters affecting the magnitude and distribution of flexural warping stresses for asymmetrical sections are explained. The basic concept of effective breadth is introduced. The effective breadth of uniform symmetrical asymmetrical face plates are presented together with the effective flexural and properties of sections. Methods are given to determine the effective breadth of curved symmetrical and asymmetrical face plates.