Seismic behaviour and three-dimensional modeling of coal gangue concrete-filled steel tubes under cyclic lateral loads

Coal gangue concrete-filled steel tube (CGCFST) is a novel type of steel-concrete composite member that provides a new approach for the resourceful disposal of coal gangue. Up to now, no investigations have been conducted on the seismic performance of CGCFST. This study, therefore, presents an investigation of the CGCFST member under cyclic lateral loads, comprising the axial compression ratios, the replacement ratios of coal gangue coarse and fine aggregates, and diameter-to-thickness ratios as the main test variables. The failure modes, hysteretic curves, stress distributions and key seismic indicators are addressed comparatively. The test results showed that the seismic behaviour of the CGCFST member is acceptable in the real-world seismic scenarios. The specimens with 100 % replacement ratios showed 13 % reduction ratios in peak lateral loads and initial lateral stiffness, and 7 % decrease in cumulative energy dissipation. An efficient three-dimensional finite element modelling method is established and carefully validated for the seismic behaviour of CGCFST members, with expanded key parameters analyzed. Finally, the applicability of the design models for the normal concrete-filled steel tube (CFST) is examined for the combined compression-bending bearing capacities of CGCFSTs.