一 100 — 
l?or double intersection trusses the formula is 
0 = 2 {n f ~ 3) ^ 
Foi. deck bridges the coiTespomliiig formulie me respectively 
(2 が— 1) 会 
C =2 ( n f - 1) J 
and C / = 2 ( が 一 1 ) ム 
It seems almost needless to say that tlio engine excess, being merely a conventional 
load, ölioulil not be used iu finding stresses in hip verticals ; but that the method 
previously given takes into account the panel engine load though not the engine 
excess. The use of all the previous formultc may always be avoided Ly employing • 
Tables III and IV, which give tlie greatest stresses clue to tlio uniform live load, 
the dead load and the engine excesses on the various members of trusses for all 
practical cases. 
The wind stress oil any windward panel of either top or bottom chord when the 
span is empty iö given by the equation 
0= ^ tf„tanö / 
and tliat on any leeward panel by the equation 
T= — ” W. 2 tan 6 ' 
where n' (not less than 登 ) is the number at that end of the panel considered which 
lies nearest the centre of the span. The corresponding wind stresses when the span 
is covered by tlio moving load can be found by substituting Tr r 8 for in the last two 
equations. It is obvious that these equations apply to thron gli, pony truss and deck 
bridges. Thoir use may be avoided by employing Table V, which gives the wind 
and ciu'Viiture stresses foi* nil practical cases. 
To asccrtaiu tlie amount of tlie transferred load when the bridge is empty. 
Let h — vertical distance between horizontal plane of shoe plates and the 
centre of gravity of the vertical projection of the trusses 
and p = total wind pressure per lineal foot of bridge on both trusses. 
Then the overturning moment will be p //, Avliicli is a couple formed by a pres- 
sure p and an equal horizontal reaction ^ » where P is the total horizontal reaction 
of the tlie four shoes and S the length of span. This must be resisted by another 
couple of e(iual but opposite moment. The forces of this couple can only be a 
