150 W. H. WAKREN. 



Ratio of area of metal to concrete = '022 



•022 x 39000 =858 fbs. per square inch. 



Rati Q ig = 2-l 



Tiie efficiency of the spiral over an equal volume of metal 

 arranged as longitudinal rods = 2*1 times as great. 



No. 3. Total compressive strength = 4517 lbs. per sq. inch. 



Resistance of spiral from last test = 1811 ,, ,, 



Resistance of concrete ... ... = 2109 ,, ,, 



Increase in strength due to 6 Bessemer steel rods \ inch 



in diameter = 297 lbs. per square inch. 



Area of rods = 6 x 0*196 = 1176. 



Limit of elasticity of metal = 37770 fbs. per square inch. 



Resistance of the rods if unstrained before testing = 



1*175 x 37770 1 lon „ . , 



— - = 1490 lbs. per square inch. 



Bence these rods did not contribute their full resistance 

 in consequence of the initial compression due to shrinkage 

 of the concrete. 



No. I. The total strength of concrete prism reinforced = 



3158 lbs. per square inch. 



Increase due to spiral = 719 lbs. per square inch. 



719 

 Here the ratio — — ■ = 0*8/ . Whereas a similar test, No. 2, 

 8j8 



gave a ratio of 2*1. 



No. 5. The total strength of the reinforced prism = 5421 



lbs. per square inch. 

 Increase clue to reinforcement = 3012 lbs. per square inch. 

 Assuming that the spiral contributed 1811 fibs, as in No. 2, 



the increase due to rods = 1201 lbs. per square inch. 



10 Bessemer steel rods f inch diameter having an elastic 



.. .. . or*™** • i 1*104x37770 



limit of 3/7/0 lbs. per square inch = ^r^ = 



29*75 

 1400 lbs. per square inch. 



