— - 97 — 
taken can bo ascertained by following out towards tlie left the system to 1 ゞ 
diagonal belongs : if the system contain the short diagonal at that end, then い 
even numbers aro to be taken, otherwise the odd ones. 
Tho difference thus found, multiplied by ^ ■ s ^— > or — — - — , as the case 
bo, will give the cload-load stress in tlio diagonal. Thus, in the diagiani, tlie 
dead- load stress in the main diagonal at the panel point 10 is 
* • [(2 + 4+ etc. + 10 ) - (1 + :]) ] ^~j h 
As in the case of the single intersection, tlie stress in a main diagonal is cqvul 
to tlie smn of tlie live and dead load stresses ; that in a counter, to tho diftVicnce 
between its live-load stress nncl the dead- load stress of tlie main diagonn-1 cu)s、iiig it 
tlie mitldlo of its length ； that iu a post of a tlirougli oi* pony truss bridge, l>> tlio 
sum of Ip/ au( | tho vertical component of tlie greatest stress iu tlie main 八 i 
( 0r ， if there be none, that in tho principal counter) attached to its upper end. 
心 batter braces belong to both systems of triangulation, tlieir stresses are tlie .’um 
the stresses found by each s 3 T stem, or by tlie formula 
: [1 + 2 + 3 + etc. • • • + ( れ 
(Tf + TFi) see a 
If tlie number of panels be even, tho calculation foi* tlie deacl-loail sti esses maj 
ho much simplified l)y coiuiting the number of panel points on tlio system coiisivloi oi 
•】>ing between the central piano and tlie panel point at tlie foot of ^ ，1,1 ^ <>11A * 
^ichuliug tlie latter, remembering that the load at the middle panel ia liahcnl, aiu 
Multiplying tlie result by W\ sec a, or W\ sec ß, . 
The finding of tlie chord stresses is also simplified when there is an even mini ei 
panels ; f oi’ they can then be calculated by tlie method explained lot* the siu r ,le 
intersection truss. 
To find the stress iu a post of a douLle-infcersectioa deck-bridge ad«l to^< tlitr 
If f and the vertical component of tlio greatest stress in tUo principal <Vug()nal 
attached to its upper end. 
J-lie stresses in hip verticals are found in tlio same maimov as in uingle-intei 
section trusses. • 
• In every clouble-intersectioii truss, there is necessarily n little ambiguity バ 01 “ 
i‘、 possible that tlio whole of the load concentrated at the first pin el point does not 
tia\el by tlie system of odd numbers ； but this ambiguity is a matteL* of small 
ext let us investigate tlie stresses clue to engine excess. In every case it ^ 
W 
better to 
assume the worst possible distribution of the loads in 
calculating tlio 
esses produced thereby. Thus iu tlie double intersection truss tlio greatest eftect 
u 1)011 tlie web members is found by pi. icing a c：u* between tlie two locomotives, '\Vile 
tlut upon the top chords usually requires tlie locomotives to be coupled togotliu . 
A^ain, in both single anil double intersection trusses tlie greatest chord stresses aic 
Stained by placing cars in front of and belli ml tlie locomotives. 
