CHAPTER IX. 
STRESSES IN LATERAL SYSTEMS AND SAVAY BRACING. 
Without making any material error the wind pressure, for the purpose of sim- 
plifying calculation, may be considered as equally distributed between the two sides 
of the bridge, although the windward side does receive the larger share. 
When the bridge is empty, the stress in any lateral rod can bo found by the 
formula 
卜 # ±i). T i^. [Eq . i] , 
anti that in any strut except those at the ends of tho lower lateral system by the 
formula 
where W is the sum of the pressures at a windwartl anti leeward panel 130 iut, ?/ the 
number of panels in the wind bracing counting in the two lacking at the ends of the 
upper lateral bracing in through bridges, ( not less than f ) the number at the 
leeward end of the rod or at either end of the strut, the panel points being marked 
as directed m the last chapter, and 〇 tho angle that tlie rods make with the struts. 
When the moving load is upon the bridge the stress in any lower lateral rod of 
a through or pony truss span or in any upper lateral rod of a deck span can be found 
by the formula 
T 
? パ ("'+ 1 ) W sec 〇 
2 n + 
n 1 - 
it — 
sec 0. [Eq. 3] 
ami that in any corresponding lateral strut, except those at the ends of the lower 
lateral system and any strut at tlie middle of the spau, by the formula 
n’ （"’ 一 1 )+", 
2 n . 
W + (»〆 一 [Eq. 4] 
* This formula is not exact, and, on account of the ambiguity iu the division of wind load 
between windward and leeward panel points, it would be difficult to make it so. It gives iu every 
case a stress greater than that which could ever come upon the strut. Tlie error is never very 
large, is greatest for the light struts near the caatre of tlie span, and roduces to uearW zero for 
the heavier struts near the end of the span. The same remark applies to Eq. 4 of this clmpter. 
