This paper studied the composite action of concrete-filled circular aluminum alloy tubular (CFCAT) stub columns under axial compression. A fine-meshed finite three-dimensional (3D) solid element model making use of a tri-axial plastic-damage constitutive model of concrete and elastoplastic constitutive model of aluminum alloy was established. A parametric study utilizing the verified finite element (FE) model was carried out and the analytical results were exploited to investigate the composite actions of concrete-filled circular aluminum alloy tubular stub columns subjected axial compression. Compared with the concrete-filled steel tube (CFCST) stub columns, the aluminum alloy tube exerted a weaker constraint effect on the infilled concrete due to its lower elastic modulus. Based on the FE analytical results and regression method, the composite action model of concrete-filled circular aluminum alloy tubular stub columns was proposed. By generalizing the stress nephogram of the concrete-filled circular aluminum alloy tubular stub column at the limit state, a design formula was proposed to estimate the ultimate bearing capacity the columns using the superposition method. The predicted results of the proposed formula show a good agreement with both the experimental and FE analytical results. The comparison between the proposed formula and current design methods indicates that the proposed formula is more accurate and convenient to use.

Thin-walled partially concrete-filled steel tubular (PCFT) columns have come to be used as the piers of elevated-girder bridges widely in Japan because of their excellent seismic performance: strength, ductility, and energy dissipation capacity. To consider this excellent seismic performance in design, it is essential to provide an analysis method to assess the ultimate behavior of the thin-walled PCFT columns by considering the cyclic local buckling of the steel tube, the behavior of the confined infilled concrete with cracks, and the interface action between the steel tube and infilled concrete. Up to the present, the shell–solid element model analysis has been the only numerical method that can be used to consider these complicated behaviors of PCFT columns in a direct manner. However, the use of this model requires unrealistically long computation time and often encounters numerical difficulty to obtain convergent solutions when applied to large structural systems such as the elevated-girder bridge systems with the multiple thin-walled PCFT piers. The objective of the present research is to propose a practical three-dimensional fiber-based model with a failure segment that is computationally efficient, yet accurate enough to assess the ultimate behavior of PCFT columns. This model was calibrated by an optimization technique, only referring to the in-plane hysteretic behavior of each single PCFT column calculated by the shell–solid element model analysis. The calibrated model is applicable to the seismic analysis of large structural systems with multiple PCFT piers under arbitrary multidirectional seismic accelerations. The accuracy and numerical efficiency of the proposed fiber-based model in the analysis of PCFT columns were confirmed extensively by the comparison to the shell–solid element model analysis results and the results of tests, such as cyclic loading tests and shake table tests.