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

232. As an example of the preceding formula, take the following:—

Assume the span as	1,000	feet.
Height of towers	100	feet.
Deflection of cables	90	feet.
Weight per foot (lineal) of bridge	2,500	lbs.
Weight per foot (lineal) of load	2,000	lbs.
Whole weight per foot	4,500	lbs.
Total weight	4,500,000	lbs.

CABLES.

The formula for the half length of cables between tops of towers is

L = b[1 + ⅔(a
b)²],

which becomes

L = 500[1 + ⅔(90
500)²] = 510.80,

which doubled, is 1021.38. To this add double the distance from the top of tower to the anchorage, (see page [206],) which is found as follows:—

tang E C G = 2a
b.

Also, tang E C G = log 2a – log b, or 2.255273 – 2.698970 = tang 9.556303 of which the angle is 19° 48′ and 90° – 19° 48′ is 70° 12′ = angle G C A or A C H.