—— 68 — 
Effeit of Wind Pres- 
sure on Chord 
StresHes. 
Initial Tcnsioiu. 
(50) per cent of that needed to resist tlie live and dead load stresses; 
the intensity of working bending stress being taken as five (5) tons, 
and that for the transferred load stress as given in Table VIII. 
In case the area required to resist tlie wind stresses exceed fifty 
(50) per cent of that required to resist tlio live and dead load 
stresses, the total section is to be obtained by adding to the former 
area one half ( J-) the latter area. 
The effect of wind pressure on bottom chord tension in double 
track bridges need not be considered, but in single tract through 
bridges tlie bottom chords are to bo proportioned first for the sum 
of the live ami dead load stresses with au intensity of live (5) tons, 
then for the sum of tlie livo load, dead load transfered load and 
wind stresses with an intensity of seven and a half (7 i) tons. If 
there bo stresses duo to centrifugal force the areas found as just 
described are to be increased by amounts sufficient to resist tlie 
last named stresses using an intensity of working stress of five (5) 
tons. 
In case of single track deck bridges the upper chords are to be 
proportioned to resist the whole of tlio live and dead load stresses, 
or six tenths ( T ^) of same plus tlie wind stresses minus the trans- 
feree! load stresses whichever of these two quantities be tlie greater. 
If there bo stresses due to centrifugal force, they are to bo ad tied to 
the greater of tlie two quantities already found. The intensity to 
be used is given in Table "VIII. Wind pressure on top chords 
of t] 11 . 011 gli bridges need never bo considered. 
It is only tlie outer bottom chords of through and pony truss 
bridges and tlio iimor top chords of deck bridges, in respect to tlie 
curve, that need to have tlieir areas increased to resist the stresses 
produced by centrifugal force. 
To allow for the stresses caused iu adjustable main members 
by tlie screwing up of tlio turn buckles or sleeve mits, tlio stress in 
each such member is to be increased by tlio amount given in the 
following table 
i 〃 Q — i.oo tons. 
1 穿 " O — 2.50 tons. 
O — I * <2 5 tt 
iF O — 2.75 „ 
卜 V’ O — 1.50 ，， 
O — 3 .。。 ，； 
O — J .75 ” 
ず O — 3.25 ,， 
ii"0— : 2 . 00 ，， 
ボ 〇 — 3.5 〇 ，， 
け " © — 2.25 ” 
^ 0-3-75 « 
2 各 " 〇 — 4 . 0 。 ” 
