Effect of the Outer Diameter on the Behavior of Square RC Columns Strengthened with Self-Compacting Concrete Filled Circular Steel Tube

This paper aimed to investigate the optimum outer diameter of square RC columns strengthened with self-compacting concrete filled circular steel tube. An experiment of twelve strengthened RC columns (SRC) and two referential RC columns subjected to axial load was presented. The variables considered in the test were the confinement index and the diameter of the strengthened section. The experimental results showed that, with the same confinement index, the material strength utilization of SRC columns dropped with the increasing of strengthened section diameter. There existed an optimum outer diameter to take full use of material strength. With the outer diameter below the optimum value, the material strength utilization increased with increasing confinement index. As the outer diameter beyond the optimum one, the material strength utilization decreased with improving confinement index.