Abstract: Recycled aggregate concrete filled stainless steel tube (RA-CFSST) have gained significant attention for their potential to enhance the mechanical behaviour of recycled aggregate concrete (RAC), especially in applications like bridge piers and marine structures. In this paper, the ABAQUS finite element (FE) software was used to analyze the behavior of RA-CFSSTs under axial compression. The stress states of stainless steel and core RAC were investigated based on reliable FE models. Stress distribution of core RAC and contact pressure between steel tube and concrete were analyzed. Afterwards, a parametric analysis was performed to evaluate the influences of concrete strength, coarse recycled aggregate replacement ratio, types of stainless steel and steel ratio on the axial compression response. Furthermore, a comparative assessment is made with existing design provisions for the CFSTs and RAC-FSTs, both domestically and internationally, based on experimental results and parametric analyses.The results show that the circumferential stress of steel tube and vertical stress of core RAC continuously increased under axial compression, indicating an obvious confinement effect. The ultimate load-carrying capacity of RA-CFSSTs is found to be primarily influenced by material strength and steel content, while the effect of recycled coarse aggregates was minor.

Key words: recycled aggregate concrete filled stainless steel tube (RA-CFSST), confinement effect, axial compression performance, finite element analysis, mechanism analysis, design provision