Influences of the strengthening methods on axial and eccentric compressive behaviors of circular concrete-filled double-skin tubular columns

Abstract

This study presents a comprehensive investigation on the compressive behaviors of concrete-filled double-skin tubular (CFDST) columns with two different types of strengthening methods (installations of reinforcement rings and steel nails). A total of five specimens were tested under axial and eccentric compression, and their damage patterns, load-displacement curves, and strain developments were studied. Results revealed that under axial compression, the ultimate load bearing capacity could be enhanced by around 15% by installing the reinforcement rings, and the occurrence of peak load could be postponed after the yielding of steel tube. This is because the reinforcement rings restrained the steel tube buckling at the loading ends. The steel nails had more contributions in ductility performance, when the column was under eccentric compression. The steel nails helped maintain the integrity of steel tubes which could provide confinement to the annular concrete to delay or alleviate the concrete deterioration and crushing failure, ultimately reducing the lateral deflection of the column. A finite element model has been developed and verified against the test results with less than 10% error in predicting the peak load capacities. The model may be used in future studies in the behavior of CFDST columns with less investigation costs.