10 Ltvi:-l.ci\i> R1 



I/,) 



. 

 ,/,- Etc> 



But by formula (5a) this becomes 



^ - C.TP, + C,H% + . . . = ZCTT. . . . (8) 



OX 



N",, TPt, etc., = sum of all of the loads to the left of 

 points 1, 2, etc., respectively, whether on the span or not. 



Afi, 3ft, etc., = moment of the same loads about points 

 1, 2, etc., respectively, whether on the span or not. 



The above formulas (6), (7), and (8) apply equally well 

 when the loading is headed from left to right in-trad of 

 from right to left, the latter being the more usual way. 

 In applying these formulas, however, it will save confu- 

 -ion inn to reverse the loading, but to turn the influence 

 line end for end, for this operation changes neither the 

 values nor the <ign> of the coefficients C. 



(IS 



The Stress S = 2C3f i- related to it- derivative -j- = 



ax 



II" in the same way that any funetinn is related to it- 



ir 



derivative. Thus, if the value of ' ' passes through zero as 



the loading advances, the stress itself may have reached 

 any one of four conditions; namely, 



1. Numerically maximum po-itive value. 



2. " minimum 



3. " maximum negative " 



4. minimum 



In practice it is desirable to find the positions of load- 

 ing to >ati-fy the fir-t and third condition-. This may be 

 done by proceeding as directed below. It i- assumed in 

 -tatiiiR the following rules that the live load is advancing 

 from right to left. In case the live load advances from 

 left to right, the wheel will be tried first to the left and 



