MAXIMUM AND MINIMUM STRESSES 



67 



PTan 



Psece 



P+ane 

 Maximum and Minimum Coefficients 



FIG. 44. 



* * 



The following conclusions may be drawn from Fig. Aj.. 



(1) All loads produce a compressive stress in the top chord and 

 a tensile stress in the bottom chord. 



(2) All the loads on one side of a panel produce the same kind 

 of stress in the web members that are inclined in the same direction on 

 that side. 



For maximum stresses in the chords, therefore, the truss should 

 be fully loaded. For maximum stresses in the web members the longer 

 segment into which the panel divides the truss should be fully loaded ; 

 while for minimum stresses in the web members the shorter segment of 

 the truss should be fully loaded. 



The conditions for maximum loading of a truss with equal joint 

 loads are therefore seen to be essentially the same as the maximum load- 

 ing of a beam with a uniform live load. 



Stresses in Warren Truss. The coefficients for maximum and 

 minimum stresses in aWarren truss due to live load are shown in Fig. 45. 



These coefficients are seen to be the algebraic sum of the co- 

 efficients for the individual loads given in Fig. 44. The live load chord 

 coefficients are the same as for dead load, and if found directly are 

 found in the same manner. 



The maximum web coefficients may be found directly by taking off 

 one load at a time beginning at the left. The left reaction, which may 

 be found by algebraic moments, will in each case be the coefficient of 



