Axial compressive behavior of round-ended coal gangue concrete-filled steel tube stub columns

Abstract

This study carried out the axial compression tests to analyze the influences of the cross-sectional aspect ratio (β), wall thickness of steel tube (t) and replacement ratio of spontaneous combustion coal gangue coarse aggregate (r) on the failure modes, load versus deformation curves and mechanical indices of round-ended coal gangue concrete-filled steel tube (RE-CGCFST) stub columns. The test results indicated that the failure modes of RE-CGCFST specimens were similar to that of round-ended concrete-filled steel tube (RE-CFST), characterized by the local buckling of steel tube and overall shear failure of the specimens; the load-bearing capacity, elastic axial compression stiffness and ductility index of the specimens were inversely proportional to the β while directly proportional to the t; with the increase of r, the load-bearing capacity of the specimens initially increased and then decreased, the elastic axial compression stiffness gradually decreased, and the ductility index initially decreased and then increased. Furthermore, a finite element analysis (FEA) model validated by the test results was employed to conduct the full-range analysis and extended parametric analysis of RE-CGCFST under axial compression. Finally, the applicability of the existing formulas of RE-CFST stub columns was assessed in calculating the load-bearing capacity of RE-CGCFST stub columns under axial compression, and then a revised load-bearing capacity calculation formula for RE-CGCFST stub columns was proposed based on the results of the extended parametric analysis.