Study on Recycled-Concrete-Filled Steel Tube and recycled concrete based on damage mechanics

The damage mechanics is for the first time applied to the research on the Recycled-Concrete-Filled Steel Tube (RCFST) and Concrete-Filled Steel Tube (CFST). A new damage model is provided and the recycled concrete and ordinary concrete are idealized to be shunt-wound and series-wound spring in this paper. The energy-absorbing capacity of recycled concrete is worse than that of ordinary concrete, because the initial damage of recycled concrete is more than that of the latter, which is verified by experiments. For RCFST and CFST, the initial damage of recycled concrete and ordinary concrete does not continue to grow, attributing to the tightening-ring force of steel tube. The energy-absorbing capacity of RCFST in the elastic range is much more than that of recycled concrete in the elastic range, and their ratio calculated based on the damage mechanics model in this paper is in agreement with the experimental results. Also, the difference of released strain energy between RCFST and CFST due to the initial damage based on the damage model is close to that based on experimental load–displacement curves of RCFST and CFST, which shows further feasibility of applying damage theory to studying RCFST.

► Damage mechanics is for the first time used for RCFST and recycled concrete.
► A new damage model is proposed for recycled concrete and ordinary concrete.
► The concrete is idealized to be shunt-wound and series-wound springs.
► The proposed damage model is verified by experiments.
► Energy-absorbing capacity of recycled concrete is worse than that of ordinary one.