2S7 
n 
肋 <1 t]i e 
UW 2 
~w ， 
corresponding end panel chord stress 
2L 
tan 6 
10 tlirusfc i neglecting the partially compensating rolling friction afc the expanding 
ot the span) is / ^ x. The compressive stress on tlic chord at t-ho fixed end, if 
6 )e an y> will consequently be given by the equation 
C = fwx~ ^ tan 0 - T 
^Pientiatiug to find a maximum gives 
differ, 
dC 
17 
e ^tiating again gives 
r ti'X J ハ 
f w j— U m 0 
o and x = ~ 
fl 
Ian 0 
w tang 
, in which X 
to the zero power, so that, when 
fl 
oc — - — - 
• tan 0 
Sl ^stitufced tlierciu, the second differential coefficient is negative, denoting a 
^^stituting 
fl 
in tl . 1m 6 
le equation giving the value of C, gives for a maximum value of the 
Com Pressio u 
wf‘ J l 
T 
2 tan 0 
sa le ' a ^ ue ^ cleduced from the Chapter on General Specifications J, is 0.07 ton 
-p[ v ? ，? t011 per h • 職 1 鼠 
19 11 lot us try the 100’ span where T = 10.9 tons and tan 0=1 
0.7 x 0.3 x 0.3 x 100 
s ho^vj 
2 
10.9 = — 7.75 tons. 
before O ni 
in ^ that the thrust cannot overcome the tension, 
Again taking the 140’ span, we have T = 16.97 and tan Q = 0.87, which 
S^ves 
X 0.8 x 0.8 X 140 
■16.97 
11.9 tons. 
s ^o\vii 
2 x 0.87 
j, AU ^ that the tendency to buckle the chord decreases as the span increases, 
t しノ 糾 118 try a 70’ span through bridge, which is the one least fitted to resist 
eth _. Here T 
6.G6 tons, and tan 〇 = 0.988, hence 
^lLA_0-3 X 0.3 x 70 6 66 _.. ilS 
2 x 0.983 0,0b 4,0 
