4 INFLUENCE DIAGRAMS 



Since the resultant moment is positive, the moment UL'(y) 

 is negative and therefore UL' is in compression. 



If the load, W2 (or W 2 ) is on the cut stringer, or between 



the verticals through E and F, the moment is, for W 2 , 



i 



. (4) 

 . (5) 



or 



M,= -W 2 (l-a 2 ) tan03 + TF 2 (&+d-a2)tan0 2 ; (6) 

 and hence 



..... (7) 



Since the resultant moment is positive the stress in UL' 

 is compressive. 

 For the load W 2 



(8) 



and UL' is in tension. 



When the load is between the cut stringer and the right 

 support of the truss, the moment is: 



M. = - W*f*9 = - W 3 (l -a 3 fj- = - W 3 (l -a 3 ) tan 3 , 



or 



M 8 = W 3 (-gk), ...... (9) 



and the member UL' is in tension. 



