—— 168 — 
Let us employ latticing for tlie top chords, batter braces, posts, and portal 
struts, and single-riveted lacing for the upper lateral struts, and bottom chord struts. 
Referring to Tables XXII. and XXIII., we find the size of stay plates for the 
top chords and batter Lraces to be x 8^ , d being a little greater than D ; that foi* 
the middle posts \ ，r x d being nearly equal to 2 1 ); tliafc for the next lai’gei 
posts ^ x 8^, d Mugless than 1.5 D but greatei* tluin 1.25 /); that for tlie largest 
posts x 8j f, , cl being a little greater than D ; that for the upper lateral struts 
i" x 7Y，， d being a little greater than 1.5 D; that for the channel lower lateral 
struts Y r x 7 ,; , d being a little less than 1.5 D ; that for the 5 f, channel lower lateral 
struts i" x d being a littlo less tlmn 1.25 D, that for the portal struts \ ,f x 5 *"， 
cl being a littlo less than 1.25 D ; and tliat foi* the bottom chord struts { r, x 9 ,f , d being 
equal to D. 
To find the thickness of the connecting or reinforcing plates at the hip we niuht 
divide the area of the section of tlie first panel length of top chortl by twice tlie suni 
of the depths of the outer and inner plates, i. e. 
26.25 
一 2(12 + 9) 
= o.g- 25 = r 
To find the length of each plate beyond tlie centre of the pin hole, let us assume 
as an approximation that the total stress on the chord is equally divided between 
the four plates, making that on eacli one about 23 tons. The lever arm for this stress 
i s 士 (g + 吾） = ふ " making the moment Ä x 23 = 12.94 inch tons. Let us use 
rivets, the working bending moment for one of wliich (vide Table XVIII .) レ 
0.494 inch ton, wliicli dividetl into 12.01 gives 27 as the number of rivets required to 
resist bending. The total pressure on tbe bearings is about 46.5 tons, and as tbß 
web (vide Table XYI.) is nearly thick tlie working bearing pressure for one rivet 
is (vide Table XVIII.) 2.G25, making the number of rivets reiiuivetl for bearing 
46.5 
2.025 
or 18 
showing that for tlie coimectiug plates of tlie top chords the rivets neetl be pi.opo い 
tioned for bending only. By making a rough sketch of the connection it is readily 
seen that we may use four horizontal rows of rivets two inches apart, and a pitch of 
3" without bringing the centres of rivet boles more closely together than good prac- 
tice allows. This arrangement will bring the end of the plate about 28" from the 
centre of the pin hole. We could make a similar calculation for the plates attache^ 
to the batter brace, but we can see that tlie same number of l.ivets will suffice, f^ 1 ' 
although tlie stress carried by each plate is less, the lever arm is greater on account 
of the greater thickness of the clianuel web. In order to allow for tlie bolt 1101 e 〇丈 
the portal strut connection we must add two or three inches to tlie length of the plate, 
so if we say that tbe total length of plate measured along the centre lines of chord 
and batter brace is 5 r , we will be pretty near the mark. 
To find tlie thickness of the connecting plates at the first joint in the top chord 
we must divide the area of one channel of the third panel by the sum of the widths 
of an inner and an outer plate. It will therefore be = 0.G : if, however, 
