Axial compressive behavior of coal gangue coarse aggregate concrete‐filled steel tubular stub columns with localized defect

During the production, processing, transportation, and preparation of steel tubes, strip‐type defects characterized by microstructural or compositional inhomogeneity may form. Additionally, localized damage to both the steel tube structure and its external anti‐corrosion coating may occur due to impacts. Such damage significantly reduces the axial load‐carrying capacity of the member, compromising structural integrity. This paper investigates the influence of defect orientation, depth, and location on the bearing capacity of coal gangue coarse aggregate concrete‐filled steel tubular (CGCACFST) columns through axial compression tests. The experimental results indicate that specimens with vertical defects exhibited severe buckling deformation at the defect location. Specimens with slanted defects experienced tearing at the defect ends. Specimens with horizontal defects showed closure at the defect site, with no significant reduction in bearing capacity. Analysis of the longitudinal and hoop strain curves revealed that the presence of defects induces an earlier transition of the CGCACFST columns into the plastic deformation stage. Furthermore, localized defects disrupt the continuity of the steel tube confinement, leading to an imbalance in the development of longitudinal and hoop strains. Finite element analysis was further employed to assess the effects of defect length, width, depth, and angle on the ultimate bearing capacity of the specimens. Based on the test data, a calculation formula for the axial bearing capacity of CGCACFST columns with localized defects is proposed. Finally, an assessment of the CO 2 emissions of CGCACFST short columns suggests that coal gangue can be recommended as a complete replacement for natural coarse aggregate in preparing concrete for non‐primary load‐bearing components in practical engineering applications.