The Architectural magazine . rably more than 9 lb.: indeed,18 lb., or 3060 tons, may be sustained on thecrown of any of thearches. This weight is sufficient to prove the strength and sta-bility of this fine structure for the safe passage over of any loads,whenever it may be erected. The great difference between Rochester Old Bridge and theproposed new one, as planned by Sir Robert Smirke, is in thethickness of the piers of the former bridge, to those of the latter,when the spans of the arches of both are considered; the onebeing three fourths of the span, the other one sixth. Waterloo Bridge.
The Architectural magazine . rably more than 9 lb.: indeed,18 lb., or 3060 tons, may be sustained on thecrown of any of thearches. This weight is sufficient to prove the strength and sta-bility of this fine structure for the safe passage over of any loads,whenever it may be erected. The great difference between Rochester Old Bridge and theproposed new one, as planned by Sir Robert Smirke, is in thethickness of the piers of the former bridge, to those of the latter,when the spans of the arches of both are considered; the onebeing three fourths of the span, the other one sixth. Waterloo Bridge. — This masterpiece of bridges, the work ofMr. Rennie, was finished and opened in the year 1817. It con-sists of nine cycloidal arches, each of 120 ft. span, with a hori-zontal roadway. Fig. 13. exhibits one arch and two piers. The span of thearch is here drawn, for convenience, more after the elliptic formthan that of the cycloid. The thickness of the piers is 20 ft., Vol. IV. — No. 36. » 66 Principles of Construction13. which is one sixth of the span of the arch. Tlie width of thepiers is from 46 ft. to 50 ft., and their height is assumed to be25 ft. The model employed for experiment was on the scaleof 1 in. to 5 ft.; and, being 4 in. wide, it equalled two fifths ofthe width of the bridjje. The model arch, when composed of voussoirs only, balancedon piers 4 in. thick and 5 in. high ; that is, on piers 20 ft. thickand 25 ft. high. When the arch had the haunches and spacesover the piers raised with wooden bricks to the level of thecrown, it balanced with 2^ lb. placed on the crown. Anotherarch, of equal and similar dimensions, being placed with onefoot on the same pier as the first, which then became a middlepier, the two outside piers being made immovable, and botharches composed of voussoirs only, either arch balanced underthe weight of 5 lb. The scale of the model being 1 in. to 5 ft., there are, in pro-portion, 125 cubic feet in 1 cubic inch; and, since 20 cubicinches o
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Keywords: ., bookcentury1800, bookdecad, booksubjectarchitecture, bookyear1834
