The Viaduct Works' Handbook

19 Road on Top, as Fig. 2. Road through, as Fig. 4. Spans. Feet. Remarks. T. C. Spans. Feet. Remarks. T. O. 10 15 20 25 30 35 40 50 00 70 80 90 100 110 120 130 140 150 175 200 Plate Girders *39 co 8 », » A ,7 97 s ‘d 9 ? s Lattice Girders b ,, » 8 » » S 27 22 J « » ” I69 ””67 „ „ 1z € „ » JE 1 2 1 15 2 7 3 2 4 7 7 0 10 0 12 10 18 0 24 10 30 5 35 15 42 0 51 0 61 10 73 0 84 10 99 0 130 0 160 0 20 25 30 35 40 50 60 70 80 90 100 110 120 130 140 150 175 200 Plate Girders, » » 1 ” " 6 Lattice Girders 3 ,, ,, 6 e » 2 » » = „ ,, leg %8 ” ” Sc » » • 29 29 68 ,, ,, os ,, M A 5 0 6 5 7 15 9 15 15 0 18 0 25 0 31 15 36 10 42 0 48 0 57 0 67 15 80 10 92 0 107 0 138 0 164 0 Another example of this class of bridge, worthy of notice, is the Velletri Viaduct, represented by the accompanying engraving, se- lected as an example of a cheap bridge, and one executed in a short space of time. This bridge is situated at Velletri, near Rome, and is con- structed to carry the railway over a deep valley. It consists of three spans of 152 feet of wrought-iron, 12 feet 3 inches deep; the total length of the bridge, including masonry abutments, 600 feet It is supported on two cast-iron piers; each pier is formed of six cast-iron columns, 90 feet high, 3 feet diameter at base, tapering to 2 feet at top, bound together with arched cast-iron girders at each 20 feet, which are covered with ornamental cast- iron fascias. The thickness of columns 1 inch; the extreme height of the bridge is 135 feet. The superstructure is for a double line of railway, which is carried on top of the girders. This bridge was erected in the short space of two months-a work unprecedented in the history of bridge making. . Setting aside the piers, the superstructure weighs about 130 tons for a span, or about 390 tons in all; or, say, 174 cwt. per foot, which, at the price of £16 per ton, is £14 per foot.