FIEE-BOX GIRDER STAYS. 237 



, I- tax I IDxl 



lYl = + 



12 12 



6 6 



and in consideration that the length of the girder is ex- 

 pressed in feet, and that the " Factor of Safety " = 6, the 

 equation becomes 



^6 12 x 6 X 6 ~ 



,, ^ Qxcxd^ xt 75 

 or, M = iDxl = — E 



6x12x6 



And substituting the proper "Modulus of Rupture" for d, 



,, , 6xb4:OOOxd^xt ^ 



6x12x6 



,, , 324000 x(Z-x« „ 

 or, M = ivxl = ^- = ±1 



432 

 or, M = tvxl = 750 xd- xt = R 



T 750 xd-xt 

 and t(j = 



I 



But as before ?(; = the total load on the supporting bolts, 

 and as in the first case 



tv = (TF-P) xDxWP, 

 and by substitution we get 



(w^- p) X i) X TFP= 152^^-^!!_^ 



I 



