CAMBKIA STEEL. 



219 



STRENGTH OF STEEL COLUMNS OR STRUTS. 



For various values of in which L = length in feet and r 



radius of gyration in inches. 



P = ultimate strength in Ibs. per square inch. 



Square bearing 

 45000 



1 + 



(12 L)* 



FOR SOFT STEEL. 

 Pin and square bearing 

 45000 



1 t ( 12L ) 2 

 1 " t "24000r 2 



Pin bearing 

 45000 

 (12 L) 2 



36 000 r 2 

 To obtain safe unit stress: 



For quiescent loads, as in buildings, divide by 4. 

 For moving loads, as in bridges, divide by 5. 



18 000 r 2 



