Behavior of axially loaded concrete columns confined by elliptical hoops

Eighteen short concrete columns reinforced with longitudinal steel and elli ptical hoops were tested to failure under monotonic uniaxial compression. T he effects of the amount of lateral reinforcement and the Shape of the elli ptical hoops on the behavior of columns were investigated. The results indi cate that elliptical hoops can provide effective lateral confinement of con crete that increases the strength and ductility of concrete The effectivene ss of such confinement diminishes as the aspect ratio, that is, the ratio o f the major axis 2A to the minor, axis 2B (designated as A/B), increases an d becomes insignificant when A/B is greater than 2.6. The strength enhancem ent is linearly proportional to the volumetric ratio of the lateral reinfor cement, but decreases linearly with the increases in A/B. The confinement f rom the elliptical hoops increases the strain at peak stress, but the incre ase is not linearly proportional to the volumetric ratio of the lateral rei nforcement.