Art. 174. PLA.TE GIRDER PORTAL KNEE BRACED. 



349 



With the center of moments at I 

 GG , ==H c+d--x l 



MI 



~d 



KK'-GG'=y 2 R 



Shear between GK and G'K'=V. 



The stresses to the right of G in the girder are statically 

 indeterminate. According to the above value of GG' the stress 

 in the bottom flange increases as x decreases. We may assume 

 that the increase from G to B is taken by GF, whence GB is con- 

 stant and equal to the stress given above for GG' when x=f, 

 therefore, 



GB==H r+^l_ V f + ^ = _ G , B , 

 d d d 



Taking a section rs with a center of moments at E, 



Horiz. Comp. of GF=H 



=V 



c+d 



d+e 



d+e 



1 -GB 



d+e 



f 



= Horiz. Comp. of G'F'. 



Taking a section rs with a center of moments at B, 



KE^H C - : ^ + ] ^-\-R+y 2 PIIoAz. Comp. GF-^- 



Taking a section pq at F, 



BF=VVert. Comp. of GF=B'F'. 



= y v e = y d 



d+e d+e 



Connections at G and F should take care of both components 

 of GF, the strut being either in tension or compression. 



The connection at E should take the stress EK and at B the 

 stress GB. In addition the connection between E and B should 



take a shear equal to V -, 



d 're 



Case No. 6b. Posts Fixed at Top and Partially Fixed 

 at the Bottom. H, V, x lJ and R t may be gotten as for the case 

 No. 4b. Then the stresses are found exactly as in the preceding 

 case No. 6a. 



Case No. 6c. This case cannot occur under the suppo- 

 sition stated at the beginning of this article. Should EB not 

 be continuous with the post, this case resolves itself into one 

 similar to No. 5, which will be treated in Art. 175. 



