317
OF ENGINEERING FOKMULÆ.
Telegraph Construction, by R, 8. BboüGH—
continued.
of its cross-section, and (2) on the material of
which it consists.
Let d = depth of the post in direction of strain.
b = width of the post at right angles to
strain.
Then, generally,
(f
m — h .-.bdz for solid posts,
m = Æ . ß . (B D3 - & tF) for hollow
posts of uniform thickness,
where h is a coefficient depending on the form of
the cross-section, and f a coefficient depending on
the material of which the post consists.
For rectangles (including squares), k = - .
For isosceles triangles (including equilateral
triangles), A = — .
41 ■
. 7T 1
For ellipses (including circles), k — — = ——- .
oZ 10*^2
In the case of thin hollow posts,
m = 2 h ./ .t . D . (D + 3 B)
where t — thickness of the material.
The following are the values of the “ modulus
of rupture ” in tons per square inch :*
* The modulus of rupture is eighteen times the load which
is required to break a bar of 1 inch square, supported at two
poiuta 1 foot apart, aud loaded iu the middle.