M = 



FIKE-BOX GIRDEK STAYS. 241 



6(w X I) 



M = 



40 

 S(iv X I) 



20 

 And as before 



so that 



M = E, 



^= 20- =— ¥" = ^ 



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

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

 equation becomes 



3(it; xl) cxd}xt 

 20~'"6xl2x6"^ 

 And substituting the proper Modulus of Rupture for c, 



j^_ ^{w X I ) 54000 xd^x t_T. 

 20 - 6x12x6 



20 X 54000 xd^xt „ 

 ^=^^-'= 3x6x12x6 =^ 



1080000 X c?^ X « „ 

 ^^^^^^^ 1296 =^ 



M=wxl = 833-3 xd^xt = R 



and w; = 833-3 xd"xt. 



But as before w = the total load on the supporting bolts, 

 and 



w = (W-P)xDxWP, 



and by substitution we get 



833-3 xd'^xt 



{W-P)xDx WP= 



I 



