一 77 — 
stress may be made of any convenient size and as thin as half (i) 
an inch. All nuts must have a uuiform bearing. 
Casti or wought iron washers must be used under the heads and 
nuts of all bolts in timber. Their bearing must bo uniform. 
Whenever possible four ( 4 ) beam hangers must bo used per 
floor beam. The screw ends are to be upset and provided with 
clieck nuts, 
Iu designing jaws special care must be taken to make tlicm and 
their connections quite as strong as the body of the strut of which 
they form a part. 
r'vo brackets or knees must be used to connect each over-liead 
strut to the posts or batter braces. 
They should be made of straight tee, angle or channel iron : if 
niade curved, no dependence is to be placed on them for either 
strength or stiffness. • 
there is no vertical sway bracing, each intermediate 
bracket must be proportioned to resist the compression induced in 
it by the wind presstiro concentrated «it the wiudward and leeward 
points of that panel of the top chord to which the bracket belongs ; 
and each portal bracket must be proportioned to resist the com- 
pi. es 81011 lnducetl in it by one half of the total pressure concentrated 
the panel points of tlio top chords. 
• The flanges at the ends of channel bars must not be cut away, 
if it be practicable to avoid doing so ； if not, there must be su 伍 cient 
1 cm forcing used to make tho strut as strong as it would have been 
^vith the flanges uncut. 
arrangement of the parts of the floor system proper, viz. 
山 6 ties, shims and guard rails with their connections must be as 
described in Chapter V. Ties must bear evenly upon their supports 
^vithoufe the aid of filling pieces. 
Finally as regards the proportioning of any structure, if cases 
should occur, which are not covered by the preceding specifications, 
lDg rule must in all such cases be adhered to: 11 Details 
must always be proportioned so as to resist every direct and indirect 
stress, that may ever come upon them under any probable circum- 
stances, without subjecting any portion of fclieir material to a stress 
greater than the legitimate corresponding working stress.” 
At each approach of every bridge there must be provided some 
fl-uangemeut to either return to the track or ditch derailed cars or 
locomotives, ^ 
No case iron is to be used anywhere, except as washers for 
timber bolts. 
field riyetting must be done with the button sett: the heads of 
e Uve ts must be hemispherical, and no rough edges mußt be left. 
Washers. 
Beam Hangerci. 
Jaws. 
Brackets. 
Cutting off the Flanges 
of Channels. 
Ties,Shiu« ami Guard 
Kail»« 
Details not previously 
mentioued. 
Re-railing Ditch- 
ing ApiKiratuf. 
Cast Iron. 
Field Ri vetting. 
