The Viaduct Works' Handbook

6 CRUMLIN Viaduct, situated in one of the most picturesque spots in the county of Monmouth, and in what is geologically termed the South Wales coal basin, is distant from Pontypool four and a half, and from Newport, twelve miles; carries the West Midland section of the Great Western Railway across the charming valley of the river Ebhw, about seven miles from the great ironworks of Ebbw Vale, Nantyglow, &c. Is an example of the class, Fig. 1, known as Kennard and Warren’s patent girders, consists of ten spans of 150 feet each, measured from centre to centre of supports, total length, including abutments, 1,658 feet, and is constructed to carry a double line of railway upon iron piers of great height, the particulars of which are given under that head. The main girders spanning the opening between supports, four in each opening, are 15 feet 6 inches deep, and placed 9 feet apart, and braced together in pairs, with a space of 6 feet between the pairs, in the manner shown by sketch. The two inner girders are made some- what stronger than the outer ones, because they carry a greater portion of the moving load, and the rails are nearer to them. The compression bars, or top flanges of these girders, are composed of rect- angular tubes, about 14 inches deep and 18 inches wide, the width and thickness of plates varying according to the strain they bear; whilst their tension bars, or bottom flanges, are of plain flat bars, 16 inches deep, arranged in two flitches, the thickness varying, those for the inner girders being somewhat strengthened by the addition of angle iron along the lower edge. The diagonals, which have to bear compressive strain, and called struts, are formed of angle and plate iron, rivetted together so that the transverse section is of the form of a cross, 10 inches by 10 inches, varying in thickness, and those which only bear tensile strain, called ties, are of plain flat bars, 9 inches wide. The floor is 26 feet wide between parapets, composed of wrought-iron cross girders, 12 inches deep, placed about 5 feet apart, at right angles to and on top of the main girders, and bolted to them at each intersection; lighter longitudinal girders are placed under each rail between these cross girders, and attached to them, so that they are even on the top; the whole surface is covered with sheet iron, 1 of an inch thick, well rivetted to them,—this forms an even surface, which is made waterproof by the application of a thick coating of hot tar and asphalte.