INFLUENCE DIAGRAMS FOR THE DETERMINATION 

 OF MAXIMUM MOMENTS 



CHAPTER I 



SIMPLE TRUSSES* 



An Influence Line for the bending moments at the 

 center of moments for any member of a truss on two sup- 

 ports for vertical loads can be constructed by a method 

 which is perfectly general in its application. The truss 

 may be of any shape, and the loads may be applied to 

 either the upper- or lower-chord joints. 



A section is passed through the truss, in the usual 

 manner, cutting the member whose influence line is to be 

 drawn. This section must evidently also cut a stringer 

 in the panel of the truss containing the cut loaded chord. 

 Let: 



d = the horizontal projection of the length of the stringer 

 which is cut by the section. This stringer will be 

 called the cut stringer. 



6 = the horizontal distance from the left support of the 

 truss to the left end of the cut stringer. 



* See " General Method for Drawing Influence Lines for Stress in Simple 

 Trusses," by Malverd A. Howe. Engineering News, June 12. 1913. 



