Art. 172. 



KNEE BRACED PORTAL. 



345 



V 



Fig. 221. (Case No. 3.) 



stress in FF' at F, and 



the stress in the web 



member connecting at 



F. In the connection at 



F' the stresses are of 



opposite kind. Similarly 



for connections at B 



and B'. 



Intermediate connec- 

 tions between B and F 



must take their portion 



of the shear and must 



hold the post in line be- 

 tween B and F. When 



the wind reverses all 



wind stresses reverse. 

 Case No. 3b. The 



stresses are found exact- 

 ly as for case No. 2 b, 



and the remarks under 



No. 3a apply. 



Case No. 3c. Cannot occur. See remarks under Case No. 2c 

 172. Case No. 4. Knee Braced Portal. Case No. 4a. Posts 



Fixed at Both Ends. 

 (See Fig. 222.) What- 

 ever pieces are inserted 

 simply for the sake of 

 appearance, or to stiffen 

 other members are not 

 considered as taking any 

 stress. A latticed portal 

 in appearance, may be 

 made of this, but only 

 the members shown by 

 full lines in Fig. 222 are 

 calculated to take the 

 stresses. The members 

 shown by dotted lines 

 simply serve to stiffen 

 the knee braces at their 

 middle. 

 Fig. 222. (Case No. 4> 



,\ ^ Po/nf of /nf/exion ^ 

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