CONTINUOUS TRUSSES 



43 



Cantilever Truss. Truss bridges which are called 

 cantilever bridges are composed of anchor spans, cantilever 

 spans and suspended spans. The simplest form of this 

 combination is shown in Fig. 30. 



Top Chord of Anchor Span. Assume any chord as UzUs, 

 Fig. 30, with its center of moments at L 2 . For loads in 

 this span the influence diagram is the base diagram rep- 

 resenting the moments m s in equation (d), since the moments 

 M L and M R are zero. 



The criterion for wheel loads in this span which produce 

 the maximum moment is 



_ 



s ls' 



(69) 



For loads in the cantilever span 

 and from equation (d), 



= 0, M R =- 



M, = -W 2 a 2 S j- = -W 2 a 2 tan 3 =W 2 ( -ef). . (70) 



