Axial compressive behaviour of rectangular DCFSST stub columns.

In this paper, a new type of rectangular double-opening concrete filled sandwich steel tube (DCFSST) is developed. This new type of composite section can keep the inner steel tubes away from the cross-sectional centroid axis through the reasonable configuration. In order to assess the structural behaviour of rectangular DCFSST members, a pilot research on stub columns under axial compression was conducted. A total of 10 specimens, including 5 with double steel square hollow sections (SHSs) and 5 with double steel circular hollow sections (CHSs), were tested with the various offset rate of inner tube (e 0) and opening ratio (ϕ). The experimental observations indicate that, generally, e 0 and ϕ have moderate effect on the failure process and failure modes of the specimens, and the failure modes of the specimens include outward local buckling of outer tube, crushing of the sandwiched concrete and inward local buckling of inner tubes. In addition, ϕ has significant influence on the load-deformation curves, axial capacity and axial compressive stiffness of the specimens; however, e 0 has no obvious effect on the above performance. Moreover, nonlinear finite element (FE) simulation on the behaviour of axially compressed rectangular DCFSST stub columns was carried out using the ABAQUS software, and the typical performance of new composite members was further analyzed by the verified FE model. Finally, the formulae to calculate the axial capacity of rectangular DCFSST stub columns were also developed based on the FE simulation results and test results. In this paper, we carry out experimental and numerical study on the axial compressive performance of a new type of rectangular DCFFST stub columns. Furthermore, based on the analysis on the finite element (FE) simulation results under different parameters, we suggest the simplified equations capable of predicting the bearing capacity of axially compressed rectangular DCFSST stub columns, and the accuracy of the formulae is verified by comparison with numerical and test results. [Display omitted] • A new type of rectangular double-opening concrete filled sandwich steel tube (DCFSST) is proposed. • Tests on axially compressed rectangular DCFSST stub columns were conducted. • Static performance of new composite columns was simulated by the finite element (FE) model. • Simplified formulae for axial capacity calculation of rectangular DCFSST stub columns were developed. [ABSTRACT FROM AUTHOR]