248 



PRACTICAL STRUCTURAL DESIGN 



bottom of the chart and go vertically upward to the curve repre- 

 senting the formula used. From this intersection proceed hori- 

 zontally to the left, where the proper fiber stress will be found. 

 Divide the load by this fiber stress and obtain the required cross- 

 sectional area of the column. If it agrees with, or is less than, 

 the area of the assumed column section the assumed section may 

 be used and the designing of the details proceeded with. Another 



I 

 i 







Fig. 162 Steel Column Formulas Used in the United States 



way is to multiply the cross-sectional area of the assumed column 

 section by the fiber stress and if this gives a carrying capacity 

 equal to, or greater than, the load the section may be used. If 

 it is less, then another section must be assumed and the work 

 gone through again. 



The steel handbooks contain tables of columns intended to 

 save the designers much of the above work. In using these tables 

 the designer will notice that values of the carrying capacities, for 

 the columns are given with the lesser and with the greater radius 

 of gyration. Be careful in using the tables to see which value 

 is used. Either value may be used in computing the effect of 

 eccentric loads, depending upon which side the load comes. The 

 smaller radius of gyration is used in determining the unit stress 



