50 INFLUENCE DIAGRAMS 



Therefore, from equation (d), 



Dividing through by s, 



M. h. fc,3 m 



*~ (82) 



*>M 



The influence diagram for - L is represented by the 



s 



base diagram drawn with CD = l. This is shown in Fig. 

 34 by the heavy line triangle. 



] Cl &! 3 

 The value of A .a is now computed for the positions 



of Wi = unity, corresponding to the panel points of the 

 truss. In the truss shown ki has the values 0, 1/5, 2/5, 3/5, 



j Cl _ fcj3 

 4/5, and 1. The corresponding values of , are laid 



off as ordinates above the line DB directly below the panel 

 points and the ends of the ordinates connected by straight 

 lines forming the polygon Dk'd'm'gB. The influence 



M 3 



diagram for ' is the shaded area shown in the figure, 

 s 



To obtain the value of M, for any particular load the cor- 

 responding ordinate in the influence diagram is multi- 

 plied by s. 



For any other center of moments as 1/2 it is only 

 necessary to draw one straight line as DA' to obtain the 

 influence diagram. 



In case the center of moments lies in a field covering 

 about one-fifth the span Zi, adjacent to the turntable, 

 the line DA will cut the polygon Dd'B and thereby indicate 



