CORRUGATED BAR COMPANY, INC. 



COLUMN TABLES 



Concrete columns are usually reinforced either with vertical bars tied together at 

 intervals by steel hoops or with vertical bars and spiral hooping. These two general 

 types of column are referred to in the tables, pages 115 to 132, as "Tied Columns" and 

 "Spiral Columns." These tables give safe loads in thousands of pounds for columns 

 to meet the requirements of the New York or Chicago building codes, or the Final 

 Report of the Joint Committee on Concrete and Reinforced Concrete. 



In New York City the code recognizes but two concrete mixes for columns, viz., 

 1:2:4 and 1: 1/^: 3, while Chicago and the Joint Committee permit, in addition to 

 these two, a 1 : 1 : 2 mix. Where it is desired to hold the column size to a minimum the 

 advantage of the richer mix is apparent. 



In the matter of percentages of vertical and spiral reinforcement it will be recog- 

 nized that it is not practicable to give all possible combinations that could be worked 

 out but there is a sufficient range in each table to satisfactorily cover most require- 

 ments. Consider, for example, the spiral columns based on New York code require- 

 ments, pages 122 to 124. For each column there is given five different percentages of 

 vertical steel and three different percentages of spiral reinforcement for each mix, thus 

 yielding fifteen load variations for one size of column. Similarly for the balance of the 

 column tables. 



The following formulas express the requirements for safe column load for each of 

 the three codes used: 



TIED COLUMNS 



New York P = Af,[l + (n - 1) p] 



Chicago P = AfAl-\-(n-l)p] 



Joint Committee P = Afc[l + (n - 1) p] 



SPIRAL COLUMNS 



New York P = fA^ - pA) + nf.pA + 2f,p' A 



Chicago P = Afo (1 + 2.5 np')[l + (n- l)p-] 



Joint Committee P = Afc [1 -{- (n — 1) p] 



In the above formulas the values of /c and n are noted in the tables. In each case 

 p represents the percentage of vertical steel and p' the percentage of spiral. The value 

 of /a in the New York formula is taken at 20,000 pounds per square inch. 



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