Study on axial compression behavior of 7A04-T6 concrete-filled aluminum tubular columns

This paper presents experimental and numerical investigations on the axial ultimate capacity of circular concrete-filled aluminum alloy tubular (CFAT) columns. 10 CFAT specimens were tested under axial load and the finite element (FE) models were developed for nonlinear analysis to verify the experiment results. The CFAT columns were fabricated by using high-strength 7A04-T6 aluminum alloys and concrete infill. The experimental results reveal that the failure of the specimen is overall instability failure, the aluminum alloy outer tube and the internal concrete demonstrate well combination function, and the specimens show high capacity and ductility. A parametric analysis was subsequently performed based on the finite element verification model to discuss the effects of slenderness ratio and aluminum ratio on the ultimate bearing capacity of the composite columns. The formulae of the standard American AA360-16 and European code EN1994-1-1 on the axial compression capacity of concrete-filled steel tubular columns were used to evaluate the ultimate strength of CFAT columns comparing with finite element models and experiments. It was indicated that current American and European codified equations fail to consider the confinement effect of the outer tube on inner concrete, which causes relatively conservative estimations results. Furthermore, EN1994-1-1 was more precise than AA360-16 prediction results, so a modified design formula was proposed based on EN1994-1-1 considering the benefits of composite function between the aluminum tube and the concrete infill. The modified formulae accurately predicted the ultimate strengths of the 7A04-T6 CFAT columns with less than 10% discrepancies.