Axial compressive behavior of stiffened spontaneous combustion coal gangue concrete-filled steel tubular column

This paper initially conducted axial compression tests on 22 spontaneous combustion coal gangue concrete filled steel tubular (SCGCA-CFST) specimens. The primary variables investigated include the substitution ratio of spontaneous combustion coal gangue coarse aggregate (SCGCA), the presence or absence of stiffeners, the longitudinal spacing between stiffeners, and the diameter of stiffeners, in order to investigate the axial compressive behavior of stiffened SCGCA-CFST. The findings reveal that while stiffeners have a minimal impact on the failure mode and the pre-peak trend of the load-axial nominal strain curve, they significantly influence the post-peak curve. Additionally, although the stiffeners exert a limited effect on the strength of SCGCA-CFST, they notably enhance its ductility and reduce both the peak value and growth rate of the transverse deformation coefficient. Furthermore, a modified constitutive model was proposed and validated against previous studies and experimental results from this study, followed by a more comprehensive parametric analysis by finite element model. Ultimately, a simplified formula for the bearing capacity of stiffened SCGCA-CFST stub column was proposed. The mean prediction accuracy was 0.99 with a standard deviation of 0.1, indicating higher accuracy compared to previous calculation methods. This study applies stiffeners to SCGCA-CFST, further advancing the engineering application of spontaneous combustion coal gangue concrete and providing both theoretical and experimental foundations.