CONCENTRIC LOADING TEST OF RC COLUMNS WITH NORMAL- AND HIGH-STRENGTH MATERIALS AND STRESS-STRAIN MODEL FOR CONFINED CONCRETE CONSIDERING COMPRESSIVE FRACTURE ENERGY

Abstract

RC columns made of concrete and steel from normal-strength up to high-strength were tested under concentric loading and the effect of each variable on confinement was studied. The localized fracture zone of post-peak region during test was also measured by embedding a deformed acrylic bar attached with strain gages inside specimens. A formalized stress-strain model for confined concrete was developed by using the effective confinement index, which was defined on test results. It is applicable to RC columns made of concrete with up to 130 MPa compressive strength and transverse reinforcement with up to 1450 MPa yield strength. Regardless of the gage length used in testing, it can be, based on the compressive fracture energy, used more extensively than the previous models.