CONTINUOUS TRUSSES 



45 



and 



7, , V T> 

 be = 1 KB =0,2 



But this expression for b'c' is the same as the coefficient 

 of W 2 in the expression for M s and hence the triangle 



DKB is the influence diagram for W 2 a2j . Since the 



12 



ordinates of the base diagram are positive and the ordinates 

 of this diagram are negative, the combination of the two 



Tan 0i =1. Tan 63 =-j. Tan 0s 



FIG. 31. 



diagrams produces the shaded area A KB as the influence 

 diagram for loads in the cantilever span. 



For loads in the suspended span the influence diagram 

 is the shaded area KBM. 



The criterion for wheel loads which produce the max- 

 imum moment is 



W 2 ' 

 Z 2 s 



(73) 



