The cyclic performance of an unbonded precast concrete segmental bridge column system is examined in this paper. This system uses unbonded posttensioning to enhance the self-centering capability and mild steel reinforcement extended across the segment joints to enhance the energy dissipation capability. A simplified analytical method for the system under lateral load is established, and the simplified analytical results are compared with those obtained from the three-dimensional (3-D) finite element method (FEM). On the basis of the simplified analytical method, suggestions are made about both the height of the column to which the mild steel should be continued from the foundation and the limitation of the steel ratio to minimize residual displacement. With the steel ratio varied, the correlation between the energy dissipation capability and the self-centering capability of this system is investigated by means of the 3-D FEM. From simulation results, it was found that both the energy dissipation and the residual displacement increase as the steel ratio increases. It was also found that the system with a steel ratio suggested by the proposed equation resulted in a significant increase in energy dissipation compared with the one without mild steel across the joints, while the recommended system maintained a small residual displacement after loading reversals.