— 98 — 
It may appear to some readers that the effect of the engine excess on the chords 
is exaggerafed, in that tho worst position is diesen, but it must bo rcra ember o cl that 
engines ai.o occasionally preceded ami lollowc.l by cars : this may not occur often in 
Japau, but it is not unusual iu America. 
Tlie greatest stresses in the top cliorJs exist when the leading engine excess is 
sit that end of tlie panel considerel lying nearest the centre of the span. The stress 
is given bj the equation 
(7=(2 n — 1) (n — — tan 0 
'm • 
for single intersection trusses wliere the panel length is not less than eighteen feet, 
or by the equation 
C = 2 ( n — 1 ) ( — n j lan 0 
when the p mel length is less than eighteen feet. For double intersection trusses 
the formula is 
¢7= [ /〆 （w —れ , ） + い’ 一 1 ) (u— れ ’ + 1 ) ] ^ tan a 
n f (never loss than ?) being the number of the panel point whore the leading engine 
excess rests. This last formula fails to give tho greatest stress in the first panel 
of tlio top choril of double intersection trasses, when the number of panels exceeds 
eleven, but as the cltov is a very small one on tlio side of clangor, ami as there aro 
seldom more th；iu ole you panels, the formula in.iy be taken as correct enough for 
nil cases. TJiC reason for the cxistcnco of the error is that iu double intersection 
trusses having more than eleven panels, tlio encl length of the top chord takes its 
Greatest stress when tlie engine excesses are separated by one panel point. 
Wlicro the nmnbor of panels is odd the engine excess stress in tlio miclillo 
panel of the top chord is the same as tlmfc iii the consecutive panels, found by mak- 
ing n r = ia tlio formula. 
The stress in the first and second panels of the bottom cliorcl in eitlicr single or 
double intersection trusses is given by the formula 
T = (2/1 — 3) ^ tan 0 [or tan a] 
except foi. the case of single intersection trusses with panels less than eighteen feet 
in longtli when it is given by 
T = 2 い — 2 ) 七 tan ク 
In single intersection trusses, where tlie panel length is not less than eighteen 
foot, tlie stress in any other panel of tho bottom chord is given by tlie equation 
T=(2 n 1 - l) ( n-w^^tan 0 
and whore it i>s less than eighteen feet, by tlie equation 
T=z 2 ("/— 1 ) (^n — n r )^ tan 0 
