Performance of recycled aggregate concrete-filled steel tubular columns under combined compression and shear load

This paper presents the behavior of recycled aggregate concrete-filled steel tubular columns under combined compression and shear load. A total of 30 recycled aggregate concrete-filled steel tubular specimens were tested, with their failure modes and shear capacities investigated. The main parameters considered include the cross-section type, the axial load ratio, the shear span-to-depth ratio, the steel ratio and the replacement rate of recycled coarse aggregates. A finite element analysis model is established, which is verified and then used to conduct analysis on the shear performance in terms of the failure modes, the full-range load-deflection relations, the stress distributions and the load transfer mechanism. The results show that both the axial load ratio and the shear span-to-depth ratio have influence on the failure modes. A strut-tie mechanism model is proposed to reveal these influences. Four failure modes are identified, while recycled aggregate concrete-filled steel tubular columns tend to fail in a shear manner with a smaller shear span-to-depth ratio and a higher axial load level. Finally, an existing simplified model is assessed to predict the shear capacity of recycled aggregate concrete-filled steel tubular columns under combined compression and shear load.