Tests on high-strength rectangular concrete-filled steel hollow section stub columns

An experimental programme on high-strength rectangular concrete-filled steel hollow section columns is reported. A total of 22 specimens were tested under concentric loading. The test variables include the material strengths (fy=495 MPa; fc′=60 and 89 MPa), cross-sectional aspect ratio (1.0-2.0) and volumetric steel-to-concrete ratio (0.13-0.17). Favourable ductility performance was observed for the specimens in the tests. The experimental results are employed to calibrate the specifications in the codes (EC4, ACI and AISC) for the design of high-strength composite columns. Comparison indicates that the specifications in ACI and AISC conservatively estimate the failure loads of the specimens by 9 and 11%, respectively. The EC4 method gives a close and conservative estimate of the ultimate capacities with a difference of 1%.