PREFACE THE primary object which the author had in view in writing this book was to prepare a text-book for students attending the first portion of his lectures on Materials and Structures; but he considers that the work may be found useful not only to engineering students in Technical Colleges and Universities, but also to those engaged in the design of constructional iron and steel work. The modern methods of determining the safe intensity of working stresses in structures have been considered in the first chapter, and have been employed more or less throughout the work. The subjects treated in the various chapters have been considered as briefly as possible, and the numerous examples given are relied upon for more complete explanation. The special feature of the work lies in the various examples which illustrate the design of the most important classes of structures in iron, steel, and timber; these have all been selected from existing works. The author's experience in teaching has convinced him of the necessity of thoroughly illustrating the various principles underlying the theory and practice of construction, as a student is never certain whether he understands these principles or not until he has attempted to apply them. The author has freely availed himself of the works of others, which he has endeavoured to acknowledge as far as possible throughout the work but he is especially indebted to the Proceedings of the Institution of Civil Engineers, the American Society of Civil Engineers, the Specifications of Mr. Theodore Cooper, M.Amer. Soc.C.E.; the works of Professors Dubois, Burr, and Waddell; also to Mr. Hickson, M.Inst.C.E., Commissioner and Engineer-in-chief for Roads and Bridges, New South Wales, for drawings of the continuous-girder road bridge, the swing bridge, and the hinged-arch bridge. Although the subject of foundations is at least as important as that of superstructures, it has only been treated briefly for pile trestle viaducts and cylinder piers. The author considers that the subject of foundations could be more conveniently dealt with in connection with a book on Engineering Construction in Brickwork, Masonry, and Concrete, which he hopes to write as soon as time will permit. In spite of the care which has been exercised in preparing this work, it is possible that in a first edition errors may have escaped detection; the author will therefore be thankful for any information as to errors in diagrams or calculations. UNIVERSITY OF SYDNEY, NEW SOUTH WALES. CONTENTS The methods of testing the strength and elasticity of materials Ductility as measured by the percentage of elongation and contraction of area Fatigue in materials Gerber's parabola . Launhardt's and Weyrauch's formulæ structures Tables of strength and ductility of various qualities of wrought iron The tensile and compressive strengths and elasticity of timber Tables of strengths of American, European, and Australian timber columns 31 Method of moments Graphic method General expression for the moment of resistance of the section of a beam Relation between the modulus of rupture and the tensile strength Examples of the moment of inertia of symmetrical and unsymmetrical sections Graphical method of determining the moment of resistance of various sections Tables of dimensions, weight, and moduli of section of rolled girders of iron Distribution of shearing stress in rectangular beams Ratio of depth to span in timber beams in regard to transverse strength and |