Art. 173. LATTICED PORTAL FOR SHALLOW TRUSSES. 347 



2nd Approximation. 



i=* \H 



a 



F=4- 



Now find D, H, and x^ as above. Having now R^ #/, H, 

 H', # t , #/ and V, the stresses are found as in case No. 4a. 



Case No. 4c. Posts Partially Fixed at Both Ends. 

 i/^^D <^ 1 <%,6-E 1 and %fc 2 /)<3f 2 <?#!. In these two test 

 equations the values of R lf H and x^ are the same as those given 

 under Case No. 4a. The approximate mean value of x^ and #/ is 



x m = 



, neglecting T T in P. 

 . Approx. 3f x '==^fet (D+approx. V) from which 



Approx. y= -- 



Now proceed as under case No. 4~b, using however equation 



(183) for R,= 



173. Case No. 5. Latticed Portal for Shallow Trusses. 



Case No. 5a. Posts 

 Fixed at Both Ends. The 

 style of portal shown in 

 Fig. 223 is used when the 

 clearance line comes but 

 little, below the top of 

 the end posts. The top 

 flange EE' is supposed 

 to be fastened to the top 

 chords of the trusses. 

 The posts may be either 

 fixed or partially fixed 

 at B and B' so, as far as 

 they are concerned we 

 may have any of the 

 three general cases. 



H, V, x lf and 3/ t 

 may be gotten as for 

 Fig. 223. (Case No. 5) case N#. 4a. 



Taking the section Im with the center of moments at C, 



-xJ -V --+M&. 



