*— *■ 1 88 — 
to that of tlie pin hole plus the product of one-half the 
depth of the bar HK by the ratio given in the table in 
Chapter VI., then drawing tho lines DE ami FG parallel 
to tlio sides of the bar, an：l at a distance therefrom equal 
to GB ; and with Cas a centre and a radius CY), equal 
to twice CB f describing an are to intersect DE and T 1 
in tli o points D and F; finally, with D and F as centres, 
and radii equal to CB, describing the arcs II L and KMi 
tangent to the sides of the bar at H and K, and to the 
outer circle at L and M. 
For welded 1 toads tlio construction is as shown in 
Fig. 2, where the pin IioIg and bar are laid out as before. 
Tho distance AB is equal to one-balf of HK multiplied 
by tlio ratio given in the table in Chapter YI., and the 
distance SO is equal to UK, or the diameter of tlie pi】 1 
hole, whichever bo the greater. The centres P and H 
of the arcs OBL and OTM respectively are found by trial ; then VE and FG 
drawn parallel to the sides of tlio bar at distances therefrom DH and FK ， equal to 
ono and seven -tenth» time VB or 11 T; and with P ami 11 as centres, and railn equal 
to two and seven- ten tlis times PB or UT y or, what is tlie same thing, equal to VU 
plus PB, arcs are described cutting DE in D, and FO in F\ finally, with D and F as 
centres, and with raan equal to DH ， arcs arc drawn tangent to the sides of the bar 
at T1 and K, and to tho arcs OBL and 01 M at L and M respectively. 
These constructions, with slight modifications, are taken from Trautwine’s 
“ Pocket-Book. M 
Next show the posts and the attached sway bracing in two projections with all 
their details. There should be allowed a clearance of about an eighth of an inch for 
tlie ends of tlie posts inside of the chord. The positions for the stay plates should 
be as close to the pin as possible, allowing a little clearance for the diagonals. Tb® 
proper positions can be ascertained from tlio general elevation. Tho lattice bars 
should bo closo to the stay plates : it will uot be necessary to show more than a 
of them on each strut, the positions of the others being indicated by tlieir centre 
lines, as shown on Plate X. 
Next show in two projections the top chord and batter brace with all tbeii* 
details, and give several views of each connecting-plate and other detail in the 
neighborhood of its position on the elevation. The joints in tlie channels and plate 
of the top chord should be located three or four inches to that side of each 
point which is farthest from the centre of the bridge, so that the pin holes sliall l^ e 
bored through a single piece, and through tlie thicker of tlio two abutting pieces» 
At the hip joint it is of course unavoidable to boro the pin hole through the abutting 
ends of the chord and batter-brace cliannels% Next pass to the plan, where the firs* 1 
thing to do is to draw parallel to the original liorizoutal line of the elevation traces 
of the central vertical planes of the trusses and of tlie central plane of the bridge ， 
locating the panel points very carefully, ami as nearly as possible vertically, belo w 
