Influence of Different Confinement Patterns on the Axial Behavior of R/C Columns

This paper studies the axial behavior of reinforced concrete columns using a new confinement technique that the first author has developed. Two opposing spirals (cross spirals) are used to confine reinforced concrete circular columns in order to enhance their strength and ductility or to increase the spiral spacing (pitch) to facilitate the flow of concrete during construction. The influence of the new confinement technique on the axial strength and ductility of reinforced concrete circular columns is experimentally investigated and compared to columns confined with conventional single spiral. Ten small-scale reinforced concrete circular columns confined with different spiral patterns were constructed and tested subjected to concentric axial compressive loading. The axial force, axial displacement and strains in the concrete and confining and longitudinal reinforcement were measured during the testing. This study showed that columns confined with two opposing spirals behaved almost similar to columns confined with single spiral when the same amount of confining reinforcement is used. The study also showed that the new confinement technique could significantly improve the axial strength and ductility of circular columns without hindering the flow of concrete during construction.