Cyclic loading tests and shear strength of steel reinforced recycled concrete short columns

This paper presents the results of cyclic loading tests on steel reinforced recycled concrete (SRRC) columns, including nine short columns and one long column. The main objective of this research is to evaluate the seismic behaviour of short columns based on the seismic tests of 10 SRRC columns under low cyclic loads with vertical axial force. The main design parameters of the columns in the tests are the recycled coarse aggregate (RCA) replacement percentage, axial compression ratio, stirrups ratio and shear span ratio. The crack status, failure modes, hysteresis loops, skeleton curves, energy dissipation capacity and ductility of SRRC columns are presented and analysed. The influence of the design parameters on the seismic behaviour of the columns is also investigated in detail. The test results show that the SRRC short column has poor ductility, as demonstrated by its brittle shear failure, and that the long column has excellent ductility, as demonstrated by its ductile flexural failure. The ductility and energy dissipation capacity of the short columns decreases as the increasing magnitude of RCA replacement percentage whilst the seismic behaviour of SRRC short columns is effectively improved by the appropriate design of the axial compression and stirrups ratio. Although the bearing capacity and stiffness of SRRC columns decreases dramatically as the shear span ratio increases, the ductility increases considerably. Based on the test and analysis results, a modified ACI design method is proposed to calculate the nominal shear strength of SRRC short columns.