346 



KNEE BRACED PORTAL. 



Art. 172. 



From equation (118) x,=x '= a ( a 



From equation (106) H=TJ'=y 2 (R-\-P) 



From equation (128) .R 1 =A > 1 '=94(.R+P) a ~ Xl 



e 



From equation (121) y^D^M^eR^ 

 From equation (122) y 2 k. 2 D.==M- 2 =Hxi' 



Frcm equation (126) V=-V'=~ [(R+P)(c-xJ+%eRi}. 



1 



Stress in KC= 



Stress in CJ"=M^+Ki'= 1 / 



s 



Horiz. Comp. CF=Q=R l 4-H=Horiz. Comp. CF'. 

 Stress in BF=- B'F'=VVert. Comp. CF=0. 

 Bending in the pests at. a and a / =i/ 2 ( J K+P)^ 1 . 

 Bending in the posts at F and F'=y 2 (R+P) (a ajj. 

 The maximum stress in the posts is at a'. 

 The connection at B takes the stress in BC and at 5', the 

 stress in B'C. 



The connection at C transfers the Horiz. Comp. of CF and 

 CF' to BB'. 



When the direction of the wind is reversed the stresses are 

 all reversed. 



Case No. 4b. Posts Fixed at the Top and Partially Fixed 

 at the Bottom. 



VzkJ)=Mi=%eRi and y 2 k 2 D<M 2 <Hx 1 



The approximate mean value of x^ and z/ is obtained from 



the equation x m = I / ^ p . ,. neglecting V in D. 

 Approximate value of #!==#/=% 



Approximate value of V= -v- [(^+P) (c ^ m )+ | 

 Dr=DL(+LL)-V D'=DL(+LL)+V 



(M 2 '-M 2 ) ] , H=R+P-H', 



