Seismic responses of multistory buildings with self-centering buckling-restrained braces: Influence of the pretension force

The post-earthquake repairability of self-centering buckling restrained braced frames (SCBFs) is usually evaluated based on structural performance indexes. From the view of the performance demands for SCBFs, further studies are urgently needed to discuss whether the self-centering brace (SCB) must be completely self-centering for the design of SCBFs. In this paper, 2-, 4-, 8-, 12-, and 16-story steel framed buildings were examined through nonlinear dynamic analyses to summarize the influence of the pretension forces of SCBs on the seismic responses of SCBFs. Numerical results illustrated that at a modest reduction of the pretension force, the SCBF satisfies both the demands on the seismic performance and the post-earthquake repairability of the building structures. The SCBF could more effectively exert the energy dissipation capacity of the self-centering brace and mitigate its floor acceleration response at a smaller pretension force. The self-centering ratio ? for the design of the SCBFs is recommended to be between 0.6 and 1.0, where ? is defined as the ratio between the pretension force of the selfcentering system and the maximum strength of the energy dissipation system. Notably, the SCB with ? = 0.6 was a partially self-centering brace, which meant that the self-centering brace was unnecessarily designed to be completely self-centering.