A COMPARATIVE STUDY ON SQUARE AND CIRCULAR HIGH STRENGTH CONCRETE-FILLED STEEL TUBE COLUMNS

This paper investigates the behavior of axially loaded square and circular high strength concrete-filled steel tube (CFST) columns. The effects of steel tube thickness and bond strength between the steel tube and the concrete core on axial load capacity and ductility are studied. The performance indices named ductility index (DI), strength enhancement index (SI) and concrete contribution ratio (CCR) are also evaluated for the square and the circular high strength CFST columns. The experimental results are compared with the values estimated by current design codes such as Eurocode 4 (EC4) and AISC-LRFD (1999). The results show that the difference of the axial load capacity due to loss of bonding is significant for both of the square and the circular high strength CFST columns. However, this difference is equal for both of the square and the circular columns with H/t or D/t smaller than 20. The EC4 design code, contrary to the AISC-LRFD (1999), generally overestimates the axial load capacity of the square and the circular high strength CFST columns.