Axial compression behavior of coal gangue coarse aggregate concrete-filled steel tube stub columns

To investigate the load -strain curves and failure modes of spontaneous -combustion coal gangue coarse aggregate (SCGCA) concrete -filled steel tube (CFST) stub columns under axial compression, 36 SCGCA CFST specimens and 18 comparative SCGCA concrete specimens were firstly tested with various SCGCA replacement ratios, concrete strengths and steel tube thicknesses. The results reveal that the bearing capacity of SCGCA CFST significantly decreases with increasing SCGCA replacement ratio, while corresponding strain increases. The addition of SCGCA can activate confining stress offered by steel tube in advance. The hoop strain of SCGCA CFST specimens increases with increasing SCGCA replacement ratio under same axial strain, resulting in enhanced confining stress. An analysis -oriented model of SCGCA CFST stub columns was then established on basis of test results, and an extended parameter analysis was further conducted using the model. Finally, the feasibility of design methods in existing design codes for evaluating bearing capacity of SCGCA CFST stub columns under axial compression was discussed.