Seismic behaviour of steel-jacket retrofitted reinforced concrete columns with recycled aggregate concrete

- Cyclic tests on steel-jacket retrofitted columns with RAC were undertaken.
- Variable Poisson's ratio of material was considered in the finite element model.
- The parametric study on the retrofitted columns was conducted.

This paper presents the experimental and numerical investigations on the seismic behaviour of steel-jacket retrofitted reinforced concrete (SJRRC) columns with recycled aggregate concrete (RAC). An unstrengthened reinforced concrete (RC) column and nine SJRRC columns tested under lateral cyclic loading are reported. The experimental results manifest that by using the steel-jacket retrofitting approach with RAC, the initial stiffness, ultimate strength, deformation ductility and energy dissipation ability of the columns are improved significantly. The peak strengths of the SJRRC columns are about 1.86-3.44 times of the counterpart of the original RC column. The retrofitted columns also show ductile post-peak load behaviour with the ductility coefficients ranging between 4.05 and 7.93. As the applied axial compressive loads increase, the failure mode of the SJRRC specimens is transited gradually from tension-controlled failure to compression-controlled failure. The specimens failed in compression-controlled mode exhibit plumper hysteresis curves, better energy dissipation ability, and higher secant stiffness than those failed in tension-controlled mode. The specimen having 100% recycled coarse aggregate replacement ratio has slightly lower lateral strength and secant stiffness than the specimens with 0% or 50% recycled coarse aggregate replacement ratio, and shows more serious pinching effect on its hysteresis curve. The effects of the preload and pre-damage of original column could be unfavourable on the cyclic performance of retrofitted column. The finite element analyses are also performed to further investigate the lateral behaviour of SJRRC columns. The proposed finite element model is validated by a comparison with the experimental results. By using the developed finite element model, parameter studies are undertaken and indicate that the applied axial compressive load and the thickness of steel jacket are the dominant factors affecting the lateral performance of SJRRC column.