## Wrought Iron Bridges and Roofs: Lectures Delivered at the Royal Engineer Establishment, Chatham |

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angle irons applied arched boom beam bearing area bearing surface bending moment bottom boom bowstring bridge bowstring roofs braced girders bracing bars Britannia Bridge calculated centre compression construction cover plate cross-beams cross-girders Crumlin curve dead load deflection depth diagonal diagram of stress diameter distance distributed load draw Engineers equal f-inch feet span flexure foot run formulae girder bridges joint lattice bridge lattice girder left abutment length limit of stress limiting stress live load longitudinal main girders maximum platform polygon proportion punched purlins rafter railway ratio reaction resistance right abutment rivet holes rolling load segment shearing area shearing force shearing stress side square foot square inch strength Stress on bar stress on boom stresses due structure struts supposed tension thickness thrust tie rod tons per foot tons per square top boom total stress truss tubular bridges vertical component w-th Warren girder weight width wind pressure

### Popular passages

Page 133 - The joints that occur in the plates of riveted girders are generally formed with cover plates. When there are several layers of plates, as in the booms of a large girder, the joints may with advantage be collected into groups, so that several may be covered by one pair of plates...

Page 142 - P* is the horizontal and P v the vertical component of the pressure on the roof. Putting P = 40 we get the following values of the normal pressure and its components, for various inclinations of the roof surface to the direction of the wind:— Lbs.

Page iv - Qui tractaverunt scientias, aut empirici, aut dogmatici fuerunt. Empirici, formicae more, congerunt tantum, et utuntur : rationales, aranearum more, telas ex se conficiunt : apis vero ratio media est, quae materiam ex floribus horti et agri elicit ; sed tamen eam propria facultate vertit et digerit.

Page 40 - In this case there is only the load on the left of j any section, and the bending moment which is the product of the load and its distance from the section, is obviously proportional to the distance of the section from the free end of the beam. The bending moment at any section a is therefore the vertical ordinate of a triangle, whose base at the abutment is equal on any scale to Wl, where W is the load and / the length of the girder or cantilever. 20. Beam supported at both ends and loaded at intermediate...

Page 135 - Hence it is that the successive combinations adopted for bridges reappear, in essentially the same forms, as roof principals. The stone-vaulted inner roofs of some of the older churches are structurally identical with masonry bridges. Timber rooftrusses are simply awkward-shaped girders, or, like the great roofs at King's Cross and over the transept of the first International Exhibition, they are timber arches analogous to those frequently erected as bridges in the earlier history of railways. Nor...

Page 135 - in the supporting framework of roofs precisely the same mechanical problem is presented as when a railway or roadway is to be carried over a ravine or river. Hence it is that the successive combinations adopted for bridges reappear, in essentially the same forms, as roof principals. The stone-vaulted inner roofs of some of the older churches are structurally identical with masonry bridges. Timber rooftrusses are simply awkward-shaped girders, or, like the great roofs at King's...

Page 92 - ... line of the Dublin and Belfast Railway, a work of about one-third of a mile in length, composed of twelve arches of blue limestone, of 61 feet span each, on the south bank, and of three similar arches on the north bank, resting on slender piers, — the tide-way being crossed by three lattice beams, a centre span of 264 feet, and two side spans of 138 feet 8 inches each, in the clear, at a height of 90 feet above high-water of spring tides.

Page 35 - ... the maximum bending moments, and consequently the maximum stresses in the chords, occur when the bridge is entirely covered with the live load ; and the greatest shear at any section, or the greatest stress in any brace, exists when the bridge is covered with live load over one or the other, usually the longer, of the two segments into which the section divides the span. A simple inspection of the tables for M and V, lately given, will show that such rules are not true for an arch. Why this is...

Page 142 - Ibs., have been at various times recorded, but the accuracy of these observations is more doubtful. We shall probably allow margin enough for the worst contingency, if the maximum pressure of the wind is assumed at 40 Ibs. per square foot of a surface perpendicular to its direction. On the inclined surface of a roof the pressure will be much less than this, the law of the variation of the pressure with the inclination being known with tolerable accuracy from the experiments of Hutton. Let P be the...

Page 54 - Thus arranged, the beam was loaded with 1-4th the known statical breaking-weight, and suffered half-amillion repetitions of loading without appreciable injury. The load was then increased to 2-7ths, and afterwards to 2-5ths of the statical breaking-weight, when the beam gave way almost immediately. It was then repaired, and suffered three million repetitions of loading with...