Experimental and numerical studies on impact behaviors of recycled aggregate concrete-filled steel tube after exposure to elevated temperature

This study investigated the impact behaviors of recycled aggregate concrete-filled steel tube (RACFST) after exposed to elevated temperatures by experimental and numerical studies. The impact test on RACFST was conducted by a split Hopkinson pressure bar (SHPB) with 100 mm-diameter. After the validation of finite element method simulation by the experimental results, parametric analysis were applied to analyze the effects of RAC strength, steel strength and steel ratio on the impact behaviors and deformation properties of the RACFSTs exposed to elevated temperatures ranging from 20C, 200C to 500C and to 700C. The results show that both the increases in RAC strength, steel strength and steel ratio significantly enhance the impact resistance of RACFST. However, when RAC strength deteriorates quickly after exposure to high temperature, the increase in RAC strength just slightly improves the impact properties of RACFST, especially after exposure to elevated temperatures higher than 500C. In conclusion, increasing steel ratio is an effective way for improving the impact behaviors of RACFST, but resulting in higher cost for practical application. For the impact design of RACFST, steel strength and steel ratio are two essential factors in terms of impact behavior enhancement and cost efficiency