STRENGTH AND ELASTICITY OF REINFORCED CONCRETE. 145 



coefficient of elasticity with increasing stress, although the 

 actual values obtained in any particular case is necessarily 

 somewhat irregular. 



Table IV. a. and Fig. IV. a., Fig. IV. a„ and Fig. IV. ft. 

 give similar results for concrete prisms 12 inches long by 

 G by 6 inches in cross-section. In IV. /?, and Fig. IV. ft, 

 the loads were carried to 1240 lbs. per square inch, then 

 gradually reduced to the initial stress of 200 lbs. per square 

 inch, producing a permanent deformation of 0*00088 inch 

 on 8 inches ; the load was afterwards reapplied and con- 

 tinued until fracture took place. Table IV. b. and Fig. IV. b. , 

 Fig. IV. c, Fig. IV. d., Fig. IV. e., Fig. IV. f., and Fig. 

 IV. h., give the results of testing prisms of concrete 24 

 inches long by 6 by 6 inches in cross-section. This series 

 of tests consists of plain concrete prisms of various propor- 

 tions of cement, sand and stone, also when reinforced with 

 longitudinal rods bound together at intervals with soft iron 

 wire and when reinforced with iron grills. The effect of 

 loading and unloading is also dealt with. 



Remarks — On the strength of concrete prisms reinforced 

 with longitudinal rods bound together with cross ties : — 



Length of prism 24 inches. 

 Cross section 6 x 6 = 36 square inches. 

 Strength of concrete prism 1:2:2 IV. b. 1, age 84 days = 

 1836 lbs. per square inch. 



Strength of concrete reinforced with 4 iron rods J- inch 

 diameter with cross ties of wire -h inch diameter — 

 average age 64 days = 2248 lbs. per square inch. 



Difference due to reinforcement = 588 lbs. per square inch. 



Area of 4 rods | inch diameter = 0*4416 square inch. 



Resistance at elastic limit = 16780 lbs. 



1 67S0 

 Resistance per square inch of prism = — — - = 466 lbs. 



per square inch. 



J— Sept. 7, 1904. 



