Another necessity of the common method of construction is the use of an unnecessary quantity of metal in the diagonals; for, by leaving them unbraced, the set of diagonals which does act is subjected to exactly twice the stress which would be caused in it if the bridge was properly constructed.  A comparison of the results of a set of calculations on the common plan with those given in this paper, shows at once that this is the case; for the ordinary system of calculation the stresses, in addition to showing compression in the verticals, gives exactly twice the amount of tension in the diagonals which they should have.

FIG. 1B.
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____________________
|
Top Flange Stresses.              |      Stresses in Diagonals. 
Hor.     Ver. |
|
C= 31.5  x 10/4.5  =         +70.00 = 31.50 |a = 70   -65         =+5.00 = 2.25
|
15.75 x 10/4.5  = 35                     |b =  "     "         =-5.00 = 4.00
\                 |
D                          > +65.00 = 22.75 |c = 65   -58.33-5    =+1.67 = 1.33
/                 |
24    x 10/8    = 30                     |d =  "      "   "    =-1.67 = 1.75
\                 |
E                          > +58.33 = 14.58 |e = 58.33-55.83-1.67 =+ .83 =  .88
/                 |
29.75 x 10/10.5 = 28.33                  |f =   "     "     "  =- .83 = 1.01
\                 |
F                          > +55.83 =  8.37 |g = 55.83-54.50- .83 =+ .50 =  .59
/                 |
33    x 10/12   = 27.5                   |h =   "     "     "  =- .50 =  .61
\                 |
G                          > +54.50 =  2.72 |i = 54.50-53.67- .50 =+ .33 =  .43
/                 |
33.75 x 10/12.5 = 27                     |j =   "     "     "  =- .33 =  .41
\                 |
H                          > +53.67 =  2.68 |k = 53.67-53.09- .33 =+ .24 =  .28
/                 |
32    x 10/12   = 26.67                  |l =   "     "     "  =- .24 =  .24
\                 |
I                          > +53.09 =  7.97 |m = 53.09-52.67- .24 =+ .18 =  .20
/                 |
27.75 x 10/10.5 = 26.42                  |n =   "     "     "  =+ .18 =  .16
\                 |
J                          > +52.67 = 13.17 |o = 52.67-52.36- .18 =+ .13 =  .11
/                 |
21    x 10/8    = 26.25                  |p =   "     "     "  =- .13 =  .06
\                 |
K                          > +52.36 = 18.33 |
/                 |
11.75 x 10/4.5  = 26.11                  |
|
L= 23.5  x 10/4.5  =         +52.22 = 23.50 |
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____________________
|
Bottom Flange Stresses.        |    Stresses in Verticals.
|
Hor.              |                              Ver. 
M same as C = 70.00              |    r = 15 — 4           = — 11.00
N    "    D = 65.00              |    s =  5 + 2.25 — 1.75 = —  5.50
O    "    E = 58.33              |    t =  5 + 1.33 — 1.01 = —  5.32
P    "    F = 55.83              |    u =  5 +  .88 —  .61 = —  5.27