Simulation of seismic behavior of square recycled aggregate concrete - filled steel tubular columns

Concrete-filled steel tubes can improve the mechanical behavior in terms of strength, stiffness, ductility and energy dissipation for the initial deficiencies of recycled aggregate concrete compared with natural aggregate concrete. The firsthand seismic performance indices on recycled aggregate concrete-filled steel tubular (RACFST) structural members are very limited due to the rare experimental results reported in the literature. To this end, a computer-assisted program for the nonlinear analysis of square RACFST columns was developed by employing SeismoStruct Software, to emphasize the effect of recycled coarse aggregate (RCA) content on the behavior of recycled aggregate concrete and the confinement effect provided by outer tubes on core concrete. Concerning the hysteretic curves, load carrying capacity and ductility, comparisons between simulation results and existing experimental ones were made to examine the rationality of numerical square RACFST model. The analysis results show that the numerical model can well simulate and predict the seismic behavior of square RACFST columns. To obtain more structural performance indices, the parametric study was performed to investigate the effects of RCA content and pre-wetting, steel yield strength, length-diameter ratio, diameter-thickness ratio, axial load ratio and structural size ratio on the hysteretic characteristic, initial lateral stiffness, ultimate lateral load and ductility of cyclic bended square RACFST columns. Both the measurement and simulation results demonstrate that concrete-filled steel tubular columns employing recycled coarse aggregates have laudable seismic behavior, and it is feasible to apply and promote the recycled aggregate concrete into concrete-filled steel tube structures in anti-seismic regions.