OF ENGINEERING FOEMULÆ.
Strains ox a Polygonal Framing.
>r
Set out on a perpendicular
line with any scale a number of
units = total weight, and from
the ends of this line lay off A' parallel to A, and
D' parallel to D, and from their intersection F lay
off B' and G' parallel to B and. C. The portions
cut off by the intersection of these lines with the
vertical line represent the weights at each point,
Wp W2, and W3, required to keep the framing in
equilibrio; and the lengths A', B', C', &c., repre-
sent the strains on A, B, C, &c.
To Determine the Character of any Strain.
Let A B al id B C be any two bars of a framing.
Produce the line AB, A C, to D and E. Let a
represent the direction of the load if it passes in
any direction between B and C, or & if it passee
in any direction between D and E; c if between
E and C; or d if between B and D.
Direc- Character of Strain
tion of I -3----------
Load.
On AB. I
----1______■
Compression
Tension i
Tension
Compression
On AC.
Compression
i Tension
1 Compression
Tension.