Axial compressive behaviour of concrete-filled double-tube stub columns with stiffeners

Concrete-filled double-tube (CFDT) columns, which are a new type of composite columns, have high fire resistance and the potential to be widely used in high-rise buildings. It is expected that the amount of steel used in a regular CFDT column will be relatively high due to the use of double tubes. To reduce the steel consumption, a thin-walled steel tube with longitudinal stiffeners may be adopted for the outer tube in a CFDT column. This paper studies the behaviour of concrete-filled stiffened double-tube (CFSDT) stub columns under axial compression. Tests on 12 CFSDT stub columns and two reference columns were carried out accordingly, and the test results confirm that the stiffened columns have high strength and good deformation capacity. A finite element model was developed to analyse the interaction between the steel tubes and concrete. Based on further parametric studies, a superposition model was proposed to predict the axial compressive strength of CFSDT stub columns.