The ductility improvement of confined concrete and steel fiber reinforced concrete is mainly due to the lateral confining effect of lateral bars and steel fiber, respectively, caused by the Poisson's effect of concrete after failure; and this effect can be related to the behavior of plain concrete under multiaxial stress states. Thus, it is quite important to obtain the complete stress-strain relation from the reliable experimental data on the post-failure behavior of concrete under low hydro-pressure, when the ductility improvement of such composite concretes is analytically discussed.
In the present study, the effects of various parameters on the plastic deformation behavior of axially loaded plain concrete subjected to low lateral confining stress were examined. The parameters used included the shape of specimen, water-cement ratio, magnitude and loading path of lateral stress, and ratio of two lateral stresses. Furthermore, the effects of the end confinement by steel ring, end friction, and steel fiber reinforcement on the plastic deformation behavior of concrete were discussed.