The effects of cross-sectional shapes on the axial performance of concrete-filled steel tube columns

Abstract Concrete-filled steel tubular (CFST) columns have been used in the construction of modern structures such as high-rise buildings and bridges as well as infrastructures as they provide better structural performance than conventional reinforced concrete or steel members. Different shapes of CFST columns may be needed to satisfy the architectural and aesthetic criteria. In the study, three dimensional FE simulations of circular, square, hexagonal, and octagonal CFST stub columns under axial compression were developed and verified through the experimental test data from the perspectives of full load-displacement histories, ultimate axial strengths, and failure modes. The verified FE models were used to investigate and compare the structural performance of CFST columns with different cross-section shapes by evaluating the overall load-deformation curves, interaction stress-deformation responses, and composite actions of the column. The extent of the ultimate-axial-strength enhancement due to enhanced steel yield strength and concrete compressive strength was evaluated through the parametric studies. At last, the accuracy of available design models in predicting the ultimate axial strengths of CFST columns were investigated. Research results showed that the behaviors of hexagonal and octagonal CFST columns were generally similar to that of the square CFST column as their overall structural performance was relatively improved.