— 103 — 
0 = {2 n’— 1 ) [n — n f )— tan O' 
''liei’o (not less than is the number at that end of the panel considered nearest 
the middle of the span. 
When the panel length is less than eighteen feet the formula is 
C = 2 (?〆 一 1) tan 0 f 
When there is an odd number of panels the stress in tlic middle panel is the 
same as that in tlie next consecutive panel. 
• The formula for the convex side chord stress clue to Fm when the panel length 
^ not less than eighteen feet is 
(2 m'-1) (h-m ，) 会 tan 6' 
where n' (greater tliau is tlie number at that end of tlie panel conaidoved furthest 
fl-01 a the middle of the ’ span. For a midillo panel, when the number of panels is 
0 山 1， tlie stress is tlie’same as for tlie next consecutive panel. 
If tlie panel length be less than eighteen feet, tlie formula is 
T = 2 (n'-l) 1 tan 6'' 
This being inapplicable to the case of a middle panel, when tlic number of panels 
1S 0( 飞 ( 1， the following formula is to be there used 
T =( ( " 2”- 1 ) IT tan e， 
As before stated these stresses clue to curvature can be found for all practical 
Cascs l) y consulting Table V. 
i'Gcapitulate : the following are the steps to bo taken in calculating tlie 
s ti esses in tlie trusses by means of the tables. 
1 • Make table of data. 
2 • Find live ami dead load stresses. 
° * 上、 iu(l curvature stresses upon one cliord, if any. 
4 P . Find wiml stresses on windward bottom chord with empty bridge. 
り 。. Find reduced dead load and the corresponding lower cliord stresses, when 
hi ■ 巧 ge is empty. 
6。. Detevmiuo whethei* the bottom cliord will require to be stiffened ； and, if so, 
wllafc «Besses it will have to resist. 
7 • Find wind stresses on windward top chord of deck bridge, or on leeward 
0 10 m chord of through bridge, when the span is covered by the moving load. 
8 • Fiud diminution of stresses on windward top chord of deck bridge, or in ere - 
nient of stresses on leeward bottom chord of through bridge due to load transferred 
a wind pressure bf thirty pounds per square foot on trusses and train. 
9 • Combine the stresses found by 2° and 3°. 
• Coinbino the stresses found by 2°, 8°, 7° and 8°. 
