Handbook of Railroad Construction; For the use of American engineers. / Containing the necessary rules, tables, and formulæ for the location, construction, equipment, and management of railroads, as built in the United States.

by George L. Vose

Let c B be half the span and c D the rise.

Join D B.

Draw n K through n perpendicular to D B.

Make B a equal to c D.

Also c e to c a.

Draw e K′ o and K a m.

K H′ and K′ are the centres, and H′ m and H′ o the lines separating the several curves.

For spans of from twenty-five to one hundred feet, the five centred arch answers every purpose; making a strong and well proportioned structure.

THICKNESS OF VOUSSOIRS, (RING STONES).

253. The thickness of the voussoir, or arch stone, depends upon the form and size of the arch, the nature of the masonry, and the character of the stone. No authority gives more reliable results than Gauthey, who, for stone of average quality, with hammer dressed beds, laid in cement, gives the following proportions between the span and depth of key:—