— 117 — 
nearest the centre of the span. 
B = the total area of the chord bars in the same panel. 
C = the gross sectional area of the chord strut. 
T == the intensity of working tensile stress for the chord bars, 
and 2V ts the intensity of tensile stress upou the gross section of the strut 
when the bars are subjected to T, and when the strut is pulling tlio 
. proper amount, 
then 
AT —GT ox T r =~ 
E be the coefficient of elasticity of the irou tlie stretch of each chord bar will be 
S- II/ 
kliere l is the panel length 
The stretch of the strut due to the stress A T will be 
S f 
Ttl 
ATI 
丸 — CE ' 
Now, if the number of panels in the span be even, the elongation of the pin hole 
at the (昝 + 1 ) 也 panel point will be 
s ~ s， =ir 
if the number of panels be odd the elongation of each pin liole nearest the 
centre of tlie span would be 
“S-S’) = ^(2 -+) 
he stretch of tbe chord bars in tlie next parcel towards tlie end of the span will 
レ as before 
Tl 
S ： 
a n(l that of tlie strut 
I 
S” 
Tl 
了: 
A f Tl 
unr 
it, as should generally be the case, tbo strut has tho same sectional area 
gom end to end of span, A == A， ， C = C , and therefore = S ’ 
or convenience of demonstration let it be assumed that the number of panels in 
le s P an is even, then tbe total stretch of the chord bars in the two panels lying 
0 one side of the middle of the span will be 2 and tlio stretch of tlie strut in tlie 
same two panels will be 2 S, ; therefore tlio elongation of tlie second pin hole from 
1 10 m Wdle should be 2 ( 5 — 夕） 
2 Tl 
= ■丨、 ” 
Similarly that of the next pin hole would be 
Pi „ . E V 2 -- C ) 
ally， if h and n f have the usual signification the elongation of the pin 1101 g at 
◊- 告） 
