SIMPLE TRUSSES 



3 



Diagonal of Pratt Truss with Inclined Top Chord. 

 Fig. 1 shows this truss and the influence diagram for the 

 member UL'. The shaded area is the influence diagram. 



To prove the construction correct, let the angles made 

 with AB by the lines AE, EF and DB be respectively 

 0i f 62 and 63, and let the distance from the left support 

 of the truss to the unit load be, in general, represented by 



Criterion, - =(Wi + Wi 1 )- = 



Tan 0i=l. Tan 02=-. Tan0=j. 



FIG. 1. 



a. While the load Wi is to the left of the cut stringer, or 

 to the left of the vertical through E, the moment is: 







, (1) 



or 



(2) 

 (3) 



