176 REINFORCED CONCRETE CONSTRUCTION 



Columns A 1 to J5 4 were squares 12 in. on a side, and C l to E 3 

 were octagons 12 in. on short diameters. The reinforced columns 

 of this series were all made with a protective shell 2 in. thick. 

 In order to study the behavior of this shell and its effect on 

 the strength of the test piece, it was removed from columns 

 B lt B 4 , and C 3 before testing. Thus B 1 and B 4 with the outside 

 shell knocked off had a cross-section 8x8 in., and C 3 when 

 stripped of its outside shell before testing had a cross-section in 

 the form of a circle 10 in. in diameter. 



Columns B and J5 4 exhibited considerably more toughness 

 than did the plain columns. These columns, outside shell 

 removed, sustained an average ultimate load of 239,50 ) Ib. 

 (3740 Ib. per square inch). A plain concrete column of the 

 same size, namely, 8x8 in. and composed of the same concrete, 



3500 



O .001 .001 .002 .003 .004. .001 .001 .002 



Deformation per unit length 

 FIG. 83. 



sustained 120,600 Ib. (or 1880 Ib. per square inch). Also, a 

 steel column similar to the reinforcement in these columns failed 

 under a load of 138,000 Ib. To quote from Prof. M. O. Withey's 

 paper before the American Society for Testing Materials, 



Volume IX, 1909: "A comparison of these figures 



indicates the value of the reinforcement and also shows a means 

 of increasing the strengths of hollow steel columns by filling 

 the inside with concrete. In the tests of columns B 2 and B 3 , 

 the area of the outside shell was so large in proportion to the 

 area of the core that the value of this form of reinforcement 



