Mechanical behavior of recycled coarse aggregates self‐compacting concrete‐filled steel tubular columns under eccentric compression

The mechanical behavior of recycled coarse aggregates self‐compacting concrete‐filled steel tubular columns (RCA ‐ SCCFST) under eccentric compression is investigated in this study. Nine specimens with different eccentricities ( e) and column length‐to‐diameter ratios ( L/D) are designed and tested, including six long columns ( L/D > 4) and three short columns ( L/D ≤ 4). Test results indicate that the long columns under eccentric compression exhibit overall flexural buckling failure, while the short columns under eccentric compression experience drum‐like bending failures. The ultimate bearing capacity of specimens decreases as eccentricity or column length‐to‐diameter ratio increases. The increase of column length‐to‐diameter ratio or eccentricity would accelerate the stiffness degradation. The ultimate longitudinal and circumference strains decrease as the eccentricity or column length‐to‐diameter ratio increases. The application of existing concrete filled steel tube (CFST) design specifications, such as American specification (AISC360‐16‐2016), Chinese code (GB50936‐2014) and Japanese code (AIJ‐1997) for the RCA ‐ SCCFST long columns are evaluated. AISC360‐16‐2016 and AIJ‐1997 are a little conservative. GB50936‐2014 is comparative accurate. Considering the influence of replacement ratio of RCA, a modified formula for predicting the ultimate bearing capacity of RCA ‐SCCFST long columns is presented in this study. The theoretical values estimated by the modified formula are in good agreement with test data.