Compressive strength of axially loaded circular concrete-filled double-skin steel tubular short columns

The confinement effect of external and internal steel tubes on sandwiched concrete in concrete-filled double-skin circular steel tubular (CFDST) short columns has a significant impact on the compressive strength and ductility of columns. Limited researches on CFDST columns have only considered the influences of a part of column parameters on the confinement effect, leading to the absence of appropriate compressive strength formulas in international standards. To comprehend the compressive behavior of circular CFDST short columns and suitably evaluate their compressive strength for practical engineering design, it is necessary to further launch the experiments on circular CFDST short columns and develop a suitable estimated formula for their compressive strength. The purpose of this paper is to develop a simple and accurate formula for predicting the compressive strength of axially loaded CFDST short circular columns with a wide range of parameters. A total of 24 specimens with outer and inner circular carbon steel tubes that withstand axial compression were tested. A new confinement coefficient reflecting the confinement effect of concrete strength in CFDST columns was proposed on the basis of the test data in the present paper and data collected from literature. Utilizing the proposed confinement coefficient, a novel strength design formula was developed to estimate the compressive strength of CFDST short circular columns. It shows that the proposed confinement coefficient can reasonably reflect the interaction effect between the sandwiched concrete and steel tubes, and the formula suggested in this paper offers better predictions of the compressive strength than current design formulas. •Tests on 24 circular CFDST short columns were conducted.•Existing strength prediction formulas were evaluated using conducted and collected test data.•New confinement coefficient reflecting the confinement effect of concrete strength was proposed.•The influences of column parameters on the confinement effects were clarified.•Novel design formula was proposed to predict the strengths of circular CFDST short columns.