CROSSARM LOAD CONVERSION 111 



endure is the resisting moment at the center divided by the total-per-pin 

 lever arm, or 57,120 pound-inches divided by 180 inches or 317.3 pounds. 

 Graph 4 is the bending moment graph of this 317.3-pound maximum load 

 per pin. 



Summary 

 Let W = Concentrated load, 

 P = Load per pin, 

 Mp = Bending moment at pole pin hole section, 

 fc = Fiber stress at center section, 

 fp = Fiber stress at pole pin hole section, 

 Sc = Section modulus of center section, and 

 Sp = Section modulus of pole pin hole section. 

 Using this notation, the results of the analyses may be summarized as 

 follows: 



For lOA arms both roofed and beveled: 



Mp = 48W (for concentrated loads) , and 

 Mp = 120P (for pin loads). Therefore, 

 48W 



P = TFo = "■''' 



For lOB arms-roofed: 



Mp = 40W (for concentrated loads) , and 



Mp = lOOP (for pin loads). Therefore, 



40W 

 P = — = 0.4W 



For the beveled lOB arm, however, where the critical section is at the 

 center, the value P = 0.4W does not apply. The value of P would be such 

 as to produce the same fiber stress at the center section as the fiber stress 

 resulting from the concentrated load (W) at the pole pin hole section. Thus 



r 180P 

 ic = —7— and 

 Sc 



fp = 



Equating these, we have 



180P 40 W 



and 



40W 

 Sp 



Sc Sp 



40W Sc _ 2ScW _ 2 X 9.52W „ ._.. 

 ^--SF^180--W~ 9 X 5.81 = ^-^^^^ 



