Wood,
a = T ÷1000
Wrought Iron,
a = T ÷ 12000
Cast Iron,
a = T ÷ 25000
As this pamphlet has to do with wooden bridges only, nothing will be said of the proper relative dimensions of cast-iron columns to sustain the strains to which they may be subjected, but a table of the strength of columns will be found further on.
Transverse Strains.
Let W = breaking weight in lbs.
" s = constant in table.
" b = breadth in inches.
" d = depth in inches.
" L = length in inches.
Then, for the power of a beam to resist a transverse strain, we shall have,