Experimental investigation on seismic performance of recycled ceramic concrete-filled double skin square steel tubular columns

Recycled ceramic concrete (RCC) is inherently brittle. However, the confinement effect of the steel tube can enhance its mechanical properties when filling it into double-skin steel tubes, yet the seismic performance of this composite structure remains uninvestigated. A seismic performance test was conducted on recycled ceramic concrete-filled double skin square steel tubular columns (RCCFDSST), with the hollow ratio and the concrete type as the principal variables. The failure patterns, horizontal load-displacement hysteresis and skeleton curves were systematically analyzed, and seismic performance was evaluated using key indicators (stiffness, ductility, strength‑degradation coefficient and energy‑dissipation capacity). The results revealed that all specimens show good ductility and energy consumption. RCC specimens matched natural concrete in lateral load‑bearing capacity and strength-degradation coefficients, but showed inferior ductility coefficients and cumulative energy dissipation. For RCCFDSST specimens, as the hollow ratio increased, lateral load‑bearing capacity and stiffness all decreased, while the average ductility coefficient and cumulative energy dissipation increased when χ ≥ 0.46. Furthermore, the applicability of existing design specifications to predict flexural stiffness and capacity of RCCFDSST was evaluated. The AIJ code provided the best prediction for initial flexural stiffness, while the flexural capacity predictions for beam-columns using T/CCES 7–2020 are conservative.