146 W. H. WARREN. 



Hence the longitudinal rods contributed rather more than 

 would be represented by the elastic limit of the material, 

 the difference is probably due to the ties. 



Strength of concrete prisms 1:2:3 IV. b 2 to IV. b 4 , age 

 79 days (mean) = 1468 lbs. per square inch. 



Total strength of prisim reinforced with 4 iron bars f inch 



diameter (mean) = 2086 lbs. per square inch. 

 Difference due to reinforcement = 618 lbs. per square inch. 



Here also the increase is greater than that of the 4 rods 

 at their elastic limit. 



The experiments on the concrete of similar composition 

 but of different ages is shown in this table and in IV. d. 

 1, 2, 3, and IV. e. 1 and 2 the effects of repeated loading 

 and unloading are shown. 



The strength of the concrete prisms IV. f. 1 and 2, con- 

 sisting of cement, sand, and f inch basalt shivers in the 

 proportion of 1 : 2 : 2 having 4 rods h inch diameter and 2 

 and 5 cross lies respectively gave a mean value of 2666 ms. 

 per square inch. The mean resistance of two similar prisms 

 not reinforced J V. d. 1 and 2 was 2007 lbs. per square inch, 

 but the age was 32 days greater, the difference 659 lbs. per 

 square inch is therefore below the amount contributed by 

 the reinforcement. The actual resistance of the four h 

 inch rods at their elastic limit is about 827 lbs. per square 

 inch, and the cross ties must have contributed something. 



The mean strength of the prisms IV. f. 2 and 3, similar 

 in every respect to the foregoing but with 4 rods f inch 

 diameter, and 10 aud 15 cross ties respectively, was 2619 

 lbs. per square inch, or a difference due to reinforcement 

 of 612 lbs. per square inch. Here the 4 rods f inch diameter 

 would contribute about 466 lbs. per square inch, leaving a 

 difference of 146 lbs. per sqrare inch to be supplied by the 

 cross ties. 



