CHAPTER III 



CONTINUOUS TRUSSES 



The Moment Influence Diagrams for various forms of simple 

 trusses have been explained in detail and found to follow 

 a single general rule in their construction. After the dis- 

 tance of the center of moments from the left support of 

 the span is determined the diagram is constructed without 

 further calculations and the ordinates are the moments 

 for unit loads, on the truss, directly above. 



For trusses which are continuous, or partially con- 

 tinuous, the moment influence diagrams are founded upon 

 the influence diagram for simple trusses. The diagram 

 for simple trusses will be called the base diagram for con- 

 venience. 



General Moment Formula. Considering any span of a 

 continuous girder, let 



M s = the moment about a center of moments distant s 



from the left end of the span. 



M L =the bending moment at the left end of the span. 

 M R = the bending moment at the right end of the span. 

 ^=the vertical shear at the left end of the span. 

 TF = any concentrated vertical load in the span. 

 a =the distance of W from the left end of the span. 

 Ri = the left reaction produced by W considering the span 



as a simple beam on two supports. 

 I =the length of the span. 



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