DOUBLE INTERSECTION TRUSSES 



39 



is constructed according to the general rule. In this 

 case the stress in U^M 3 is not equal to the ordinates of the 

 diagram divided by the lever arm s+b+d, since a portion 

 of each ordinate corresponds to the moment of the stress 

 in the diagonal M 2 L B . The simplest way to utilize the 

 influence diagram is to first determine the stress hi C7 3 M 3 

 for a unit load at L 3 . (This can be very quickly done 

 graphically.) Then below F in the influence diagram lay 



FIG. 29. 



off to any convenient scale the distance Fg equal to this 

 stress. Draw a straight line through B and g and extend 

 it until the point D is located. Complete the diagram 

 according to the general rule. The ordinates in this 

 diagram correspond to the actual stresses in the piece 

 UaMa produced by a unit load moving across the span. 



Lower Segment of Vertical in the " K " Truss. As in the 

 case of the upper segment it is impossible to make a section 

 which does not cut at least four members of the truss. 

 Practically the same method is employed as outlined for 



