Testing, Modeling, and Application of a Two‐Stage Self‐Centering Brace for Seismic Resilience Enhancement of Rocking Core System

ABSTRACT Self‐centering devices have been shown to be effective in reducing residual story drift after an earthquake. However, they typically result in high floor acceleration demand, especially in applications with rocking core systems where the stiff rocking core enhances the stiffness for higher‐mode and induces acceleration amplification. To address this limitation, this study proposed a novel two‐stage self‐centering brace (TSSCB), providing an available alternative for balancing the trade‐off between floor acceleration and post‐earthquake residual drift. The TSSCB features a two‐stage mechanism controlled by a gap configuration, enabling energy dissipation through slip friction under low‐intensity earthquakes and reducing post‐earthquake residual story drift using shape memory alloy (SMA) cables under high‐intensity earthquakes. The paper first introduces the detailed configuration and working principles of the TSSCB. Cyclic tests on eight TSSCB specimens demonstrate stable hysteretic behavior, where the device behaves similarly to traditional friction dissipators under small displacements and exhibits delayed flag‐shaped hysteretic loops under large displacements. The effects of SMA cable pre‐tension levels and loading protocols on cyclic behavior are discussed, and the low‐cycle‐fatigue performance of the TSSCB is evaluated. A phenomenological hysteretic model is developed to describe the cyclic behavior of the TSSCB, followed by nonlinear time history analyses of five archetype rocking core‐moment frame systems to validate the TSSCB's application. The results indicate that incorporating an appropriate value of gap into the TSSCBs can reduce floor acceleration without significantly increasing residual inter‐story drift, highlighting the TSSCB's advantage for multi‐objective seismic control and resilience enhancement of buildings.