Experimental Study on Axial Compressive Behavior of CFST Short Columns Confined by Carbon Fiber Reinforced Polymer Composites

This paper portrays an experimental study to understand the compressive performance of FRP-confined concrete-filled steel tube (FCCFST). Columns CFST columns have large strength and good deformability characteristics which make it precious structural members. The large lateral stiffness and strength, as well as the large load-carrying capacity that is obtained by a steel tube and concrete interaction, are sufficiently procured in the CFST columns. Concrete-filled steel tube columns are promoted for superior performance due to the composite action between the concrete core and the steel tube. However, the full potential of this composite action is often not realized because of the differing dilation properties between the materials, which could lead to debonding at the interface. To address this issue, external confinement using FRP is proposed to enhance the bonding between the concrete and steel tube. In this study, seventy-two columns were verified to examine the effects of various factors, including the number of carbon fiber reinforced polymer (CFRP) layers, steel tube thickness, and infilled concrete properties (with and without silica slurry and polypropylene fiber) on the columns' load capacity and axial deformation capacity. The experimental load-carrying capacity of the columns was also compared with those obtained from existing formulations proposed by some researchers. It is observed that the external CFRP wrap helps constrain the steel tube's outward local buckling deformation and enhances the concrete core's confinement. The results also demonstrate that CFRP confinement significantly improves the load capacity and axial distortion capacity of the CFST columns. The prediction performance of existing formulations was varied, however, one of the proposed ones estimates the experimental values with reasonable accuracy.