To improve the seismic performances of reinforced concrete (RC) bridge columns and to prevent columns from shear failure and core concrete crushing, high strength concrete filled steel tube (CFST) is put into RC columns to form a new kind of composite column. Through cyclical loading tests, the seismic performances of four columns are studied. The first column tested is a conventional RC column, the second one is a bonded composite column, the third one is an unbonded composite column, and the fourth one is an unbonded composite column whose axial force is composed of only bone by its CFST column. The test results show that the CFST column can increase the flexural strength, displacement ductility and energy dissipation capacity, and decrease the residual displacement after undergoing large deformation. When the degree of bond between the steel tube and the outside concrete around the tube is reduced, the load-carrying capacity of the composite column decreases, but the ductility increases. When the axial force is only bone by the CFST column, the load-carrying capacity of the composite column decreases significantly, and the ductility increases markedly.

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