Steel fiber reinforced recycled aggregate concrete filled steel tubular (SF-RACFST) column is a new type of eco-friendly composite component. It is commonly subjected to combined bending and shear in practical engineering, while its failure mechanism and bearing capacity calculation method remain immature. Aiming at the deficiencies of existing researches on the performance degradation of recycled aggregates, damage evolution and bending-shear cooperative working mechanism, experimental and theoretical studies on the bending-shear response of SF-RACFST columns were carried out based on acoustic emission (AE) technology. A total of 26 specimens were designed with five variable parameters, including steel tube thickness, replacement ratio of recycled coarse aggregate, volume fraction of steel fiber, shear-span ratio and axial compression ratio, and shear loading tests were conducted. The AE signals of specimens during the whole loading process were monitored in real time. By analyzing RA-AF parameters, cumulative energy and b-value, the evolution laws of micro-crack initiation, propagation and macroscopic failure of recycled concrete were revealed, and the inhibition mechanism of steel tube confinement and steel fiber bridging effect on damage accumulation was clarified. Combined with the classical yield criterion, the steel-concrete interface slip and the triaxial stress state of core concrete were analyzed. A theoretical model for bending-shear bearing capacity was established considering the performance degradation of recycled aggregates and the strengthening effect of steel fibers. The test results indicate that steel fibers can effectively improve the peak strength and ductility of recycled concrete and reduce the damage accumulation rate. Increasing the steel tube thickness can delay the local buckling of steel tubes obviously. Comparative verification between theoretical results, existing design codes and test data shows that the proposed formula has high calculation accuracy and low discreteness, and can reasonably reflect the influence of key parameters, which is superior to the formulas in current codes. This study enriches the damage monitoring theory of SF-RACFST composite columns, and provides important theoretical basis and calculation method for the engineering design and safety evaluation of such new components.
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Ma et al. (2026) studied this question.
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