Study on the hysteretic behavior of recycled aggregate concrete-filled steel tube columns containing ferronickel slag

Abstract To study the hysteretic behavior of recycled aggregate concrete-filled steel tube (RACFST) columns containing ferronickel slag (FNS), this paper designed and fabricated nine specimens with the recycled coarse aggregate replacement ratios (RCAs), diameter-thickness ratio, and axial load ratios as the design parameters, which were tested using low-cycle reciprocation loading tests. The damage patterns of all specimens were observed; the hysteresis and skeleton curves of each specimen were obtained. Comparative analyses of the ultimate strength, hysteretic behavior, ductility, stiffness degeneration, energy dissipation capacity, and other seismic parameters were performed. Additionally, a series of numerical models of RACFST columns were established and the relevant parametric studies were discussed. The test results showed that the damage position of the specimen was located in the plastic hinge area at the bottom of the column, which was mainly characterized by the bulging and fracturing of steel tubes. The hysteresis curves of all specimens were relatively full, and the RCAs had a negligible influence on the hysteretic behavior of the columns. With the increasing axial loading ratio, the degeneration rates of ultimate strength and stiffness were accelerated, the deformation capacity was inversely deteriorated, while the hysteretic energy dissipation was unexpectedly enhanced. As the diameter-thickness ratio declined, both the ultimate strength and ductility of the columns were improved accordingly. Furthermore, an applicable numerical model was established and compared with the test results. The numerical results were in good agreement with the test results and especially could reflect the hysteretic behaviors of columns. Moreover, the results obtained from the parametric analyses showed that the slenderness ratio , axial load ratio, and steel ratio all exhibited a relatively large effect on the ultimate strength and ductility of the specimens, while the effect of the RAC strength was relatively small.