Effects of Reinforcements on Ductility of Concrete

To study and compare the reinforcing action of stirrups, randomly distributed short fibers, and compression reinforcement in improving ductility of plain concrete, over-reinforced and under-reinforced beams and prisms were tested in continuously increasing as well as cyclic loading. Reinforcement appears to increase ductility primarily by retarding growth of longitudinal microcracks. As a result, although overall ductility of over-reinforced beams was improved by the addition of compression steel, its presence did not significantly influence the behavior of concrete in the compression zone. Stirrups and fibers substantially improved the ductility of concrete as evidenced by the increased ultimate compressive concrete strains and toughness. Spacing of reinforcement appears to have a small influence on cracking and on ductility for a spacing less than about 1 in. Only small size beams and prisms were tested in this investigation.