Tests of Collared Concrete Columns under Eccentric Axial Load

One strategy for the rehabilitation of existing reinforced concrete columns is to target the improvement of specific local vulnerabilities in the columns related to inadequate strength or ductility. Eight full-scale columns were tested to evaluate the performance of a rehabilitation technique for square or rectangular reinforced concrete columns using a system of discrete external steel collars. Unlike other external confinement methods such as steel jacketing and fiber-reinforced polymer (FRP) wrapping, the proposed collar system exploits the benefits of confining elements with significant flexural stiffness. The project investigates the effectiveness of steel collars for rehabilitating columns when they are loaded axially at an eccentricity from the column centroid. Parameters investigated include collar spacing, collar flexural stiffness, active confining pressure, and load eccentricity. The columns were tested under monotonically applied axial loading and exhibited both strengths and ductilities well in excess of what would be expected with conventionally reinforced columns.