Shape effect on axially loaded CFDST columns

Concrete-filled double skinned steel tubular (CFDST) columns have been used to construct modern structures such as tall buildings and bridges as well as infrastructures as they provide better, lesser weight, and greater stiffness in structural performance than conventional reinforced concrete or steel members. Different shapes of CFDST columns may be needed to satisfy the architectural and aesthetic criteria. In the study, three-dimensional FE simulations of circular and elliptical CFDST 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 CFDST columns with circular and elliptical cross-section shapes by evaluating the overall load-deformation curves, interaction stress-deformation responses, and composite actions of the column. At last, the accuracy of available design models in predicting the ultimate axial strengths of CFST columns were investigated. Research results showed that circular and elliptical CFDST column behaviors were generally similar. The overall structural performance of circular CFDST columns was relatively improved compared to the elliptical CFDST column.