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

168. Mr. Hodgekinson gives, as the result of his experiments, the following formula for dimensioning the cast-iron girder above referred to.

W = 26ad
L,

Where W is the breaking weight in tons,

a the area of the bottom flange,

d the depth of the girder in inches,

L the length in inches.

As it is not considered safe to load a cast-iron beam with more than one sixth of the breaking load, the formula may be expressed as follows:—

W = 26ad
6L,

for the weight in tons which may be safely borne, and transforming

a = 6WL
26d