STRENGTH AND ELASTICITY OF REINFORCED CONCRETE. 141 



fracture occurred, and the extremity of the head of the 

 specimen, considerably greater stresses would have been 

 sustained, and fracture could not then occur until the 

 elastic limit of the metal reinforcement was reached. The 

 stresses developed in the metal rods varied considerably, 

 but assuming the extensions of the concrete, within the 4 

 inches length upon which measurements were taken, to be 

 the same as the metal embedded in it, (which was not true 

 in many of these tests), the stresses may be calculated as 

 follows : — 

 Let P = the total pull on the metal reinforcement. 



p = the intensity of stress on the metal. 



E — the coefficient of elasticity of the metal. In 

 this case Bessemer steel = 30,000,000 lbs. 

 per square inch. 



A = the extension per inch. 



a = the area of the reinforcement in square inches. 



Thenp= - = AE 

 a 



In I. a. 1, Table I., 5,000 lbs. pull produced an extension 

 = 0*000131 inch per inch. The breaking load 5696 lbs. 

 produced A = 0*00015 inch, a = 0*1963 sq. inches. 



.*. p = 4500 lbs. per sq. inch and P = 883 lbs. 



.*. 5696 - 883 = 4813 lbs. sustained by the concrete, or 

 about 300 lbs. per square inch. 



In I. a. 3, Table I. A = 0*00014 inch, a = 9815 sq. inches. 



.*. p = 4200 lbs. per sq. inch, and P = 4122 lbs. The 

 breaking load was 8256 lbs., and the load sustained by the 

 concrete 4134 lbs. or 258 lbs. per square inch. 



The rods used to reinforce the tension were in every 

 case of Bessemer steel, having an elastic limit of 42,000 lbs. 

 per square inch and a coefficient of elasticity of 30,000,000 

 lbs. per square inch. 



