SPECIFICATIONS FOR STEEL HIGHWAY BRIDGES. 43 
Bottom chords composed of angles preferably shall 
be constructed with the vei-tical legs of the angles ex- 
tending downward. 
For compression members formed of side segments and,.^^^- }lJ^Sr^,if„^ 
a cover plate, the workmg Ime shall comcide as nearly as axes. 
K practicable with the gravity axis of the section. For 
---^ symmetrical sections the working line shall coincide with 
the gravity axis. For two-angle bottom chord or diag- 
onal members the working line may be taken as the gauge 
hne nearest the back of the angle. 
Trusses shall, in general, be given a camber by in- ^^- camber. 
creasing the length of the top chords an amount in each 
panel length equal to -^ inch for each 10 feet of their 
horizontal projection. 
Pin-connected trusses shall have stiff riveted members ^^^^ &^pi™c^". 
in the first two main panels of the bottom chords at each nected trusses. 
end of the span, and all web members performing the 
function of suspenders shall be of stiff riveted construc- 
tion. 
Rigid counters are perferred. Adjustable counters, ^^l' '^aXStabie 
when used, shall have open turnbuckles, and in the de- members. 
sign of these members an allowance of 10,000 pounds shall 
be made for initial stress. Only one set of diagonals in 
any panel shall be adjustable. Sleeve nuts and loop 
bars shall not be used. 
Eyebar heads shall have a cross-sectional area through ^^- Ey^^ars. 
the center of the pinhole exceeding that of the body of the 
bar by at least 40 per cent. Tlie net section adjacent to 
the head shall be not less than that of the main body of 
the bar. The thickness of the bar shall not be less than 
ys Oi the width and not greater than 2 inches. The form 
of the head shall be submitted to the engineer for ap- 
proval before the bars are made. The diameter of the 
pin shall be not less than two-thirds of the width of the 
widest bar connected. 
The eyebars of a set shall be packed symmetrically^ ^^^j^^J^^'^''^^^^ 
about the central plane of the truss and as nearly parallel 
as practicable, but in no case shall the inclination of any 
bar to the plane of the truss exceed ^ inch per foot. 
Bars shall be packed as closely as practicable and held 
against lateral movement, but they shall be arranged so 
that adjacent bars in the same panel will be separated by 
at least % inch. 
All intersecting diagonal bars not far enough apart to 
clear each other at all times shall be well clamped to- 
^ gether at intersections. 
Steel filling rings shall be provided, when required, to 
prevent lateral movements of eyebars or other members 
connected upon pins. 
Diaphragms shall be provided in the trusses at the end ^^- Diaphragms. 
connections of all floor beams. In general, such dia- 
phragms shall extend down to the bottom flange of the 
floor beam and for at least two rivet spaces above the 
top flange. 
