Effects of Confinement in Circular Hollow Concrete Columns

Abstract

The strength and ductility of concrete can be improved by adding confinement, which helps RC structures to withstand extreme loads in a ductile manner. However, the confined concrete behavior in hollow sections is not well understood, and thus this paper presents a systematic computational study on the confinement effect in hollow sections using key parameters such as the concrete dilation and confining pressure. Computational results show that the confinement effect on solid and hollow sections is very different. This difference is due to variations in concrete dilation and the distribution of confining pressure across the cross section. It is further shown that for circular hollow columns with a wall thickness ratio of .1, one layer of transverse reinforcement provides a satisfactory confining effect. For columns with larger wall thickness ratios up to .2, two layers of reinforcement connected with crossties are more appropriate, with an inner∶outer reinforcement ratio of 1∶9.