—— 1 4 1 
will be more rivets than necessary ； but such a bearing should not bo counted upon. 
Tlie rules for proportioning shoe, roller and bed plates are givon in Chapter VI. 
At the iutennodiate stmt connection, there should be enough rivets used in 
respect to bending and bearing to transfer the calculated stress upon the strut to 
tlle connecting plates. 
The method of determining the dimensions and number of rivets for extension 
plates on the npnor ends of posts is similar to that explained lor splice or connect- 
ing plates. 
The thiclvness of tlie re- enforcing plates at the lower end of a post is determined 
by tlie Leaving required; and tlieir length in the manner already clesoribed. The reason 
for cutting away the bottoms of the post channels is merely to p ick the chord more 
closely, and thus reduce the bending moments on the pins. But, if tho method of 
P m Proportioning recommended be adopted, tlie necessity for cutting away the chan- 
nels， to any extent, vanishes ; for at the middle of tho span the web stresses are so 
sma 】 l ， 认妣 their moments aro neglected, and the pins at the feet of the other posts 
have aa excess of strength. 
When, because of their large diameter, the lateral rods cannot be attached to 
the clioixl pins, but must be connected by vertical pins passing through the lateral 
^ nit jaws, they must be made to pull on the middle point of each of the latter pins 
y using a double eye on one of tho rods, with a space between large enough to 
a ^mit tlie eye of the other rod. This is to avoid all tendency to rotate the lateral 
s tnU about its axis. The rods can be retained in place by fillers above and below. 
With this detail, there is a tendency to break the jaw through the pin holes, 
because of the moment of the longitudinal component of the lateral rod stress : 
二 e jaw plate must therefore be made wide enough to properly resist this moment. 
f easiest way to proportion the plate is to assume its dimensions, and to fmd its 
^Gsistancc to bending, neglecting the area lost by the pin holes (which area is" close 
0 ヲ ie neuti-al surface), and making up for the omission by providing a little extra 
resistance. 
To illustrate the method, let us take a two-inch lateral rod, making an angle of 
01 ^ 7 *^ ve Negroes with the planes of tlie trusses, and let the distance between cen- 
/es of pi n bearings be six inches. The stress on such a rod is 8.14 x 7.5 — 23.55 
0 ns, ami the bemliag-momenfc on tlie pin is ^ x 23.55 x B = 85.3 inch tons, coi •- 
iespon(Ji U g (vide Table XIV) to a diameter of three inches and a fourth. The dis- 
fuace from tlie axis of the pin to the centre of tlie jaw bearing will bo about 
« •+ 2" + i” + 吾" = め The longitudinal component of the stress on the lateral 
.° 18 23.55 x 0.7 = 10.5 tons, making the moment on the jaw about 5 x 16.5 = 82.5 
C 1 tons. The thickness of the jaw plate should be and let us assume the width 
The resisfcing-niomenfc is given by the well-known formula, 
to be 7" 
M= 
where II 
gives 
m 
: て’ 
11.25 tons, I = ^b(P = T \ x x (7) n , and d x 
Substituting, 
