DOUBLE INTERSECTION TRUSSES 



35 



of three diagrams for simple trusses. For the truss shown 

 C" falls in the line CB. This method of constructing the 

 influence diagram requires no preliminary calculations. 



As in the previous case the position of wheel loads 

 producing the maximum moment is best found by trial. 



Lower Segment of Diagonal in Sub-divided Double Tri- 

 angular Truss. Selecting the member L 4 M 3 , Fig. 25, it is 

 at once seen that it forms a part of the diagonal of the truss 



E D"E" 



shown by full lines and also a part of the auxiliary truss 

 L^M^LQ. The influence diagram for vertical shear, neg- 

 lecting the effect of the auxiliary truss, is DeD"B"mnopBD. 

 The shear diagram for L^M 3 as a member of the auxiliary 

 truss is D"F"B"D". This is constructed according to 

 the general rule using the line D"B" as the line DB in the 

 usual diagram. The influence diagram for LM$ now 

 becomes the shaded area in Fig. 25. 



The position of wheel loads producing the maximum 

 vertical shear is found by trial. 



Chords of the "K" Truss. The truss shown in Fig. 

 26 is called the " K " truss since the web members form 



