Bridge pier failures during earthquakes usually start with the formation of plastic hinges. In order to enhance member efficiency in the post-buckling stage, the deterioration rate must be controlled and reduced. This paper presents experimental information on the cyclic behavior of steel box piers with added internal strengthening devices. Test results show that the strength and elastic stiffness of the upgraded members stay at levels equivalent to those of the original members, however, the energy dissipation capacities of such members are substantially increased and the rates of strength deterioration are significantly reduced. Relationships between performance enhancement of members and characteristics of strengthening devices are also reported.