Chapter 7, Problem 7.52QP

Two 6 in. × 12 in. concrete cylinders with randomly oriented steel fiber contents of 0 and 2% by weight, respectively. After curing for 28 days, the specimens were subjected to increments of compressive loads until failure. The load versus deformation results were as shown in Table P7.52.

TABLE P7.52

Specimen no.	1	2
Fiber content (%)	0	2
Deformation (in.)	Load (kips)
0	0	0
0.012	114	114
0.024	145 (failure)	153
0.036		130
0.048		89
0.060		76 (failure)

Assuming that the gauge length is the whole specimen height, determine the following:

1. a. The compressive stresses and strains for each specimen at each load increment.
2. b. Plot stresses versus strains for the two specimens on one graph.
3. c. The initial modulus of elasticity for each specimen.
4. d. The ultimate strength for each specimen.
5. e. The strain at failure for each specimen.
6. f. Toughness. Curves may be approximated with a series of straight lines.
7. g. Comment on the effect of adding fiber on the following:
   1. i. Modulus of elasticity
   2. ii. Ultimate strength
   3. iii. Ductility
   4. iv. Toughness