Steel concentrically braced frames (CBFs) are an efficient, stiff lateral force resisting system but have limited ductility capacity. Conventional CBFs have limited ductility capacity due to brace buckling. A new building frame system known as a Self-Centering CBF (SC-CBF) that has large ductility capacity and minimal residual drift under earthquake loading is being developed and has been extensively evaluated using hybrid earthquake simulation at Lehigh University's NEES Equipment Site. The ductility capacity of the SC-CBF system is increased by allowing the frame to rock on its base. High ductility vertical post-tensioning (PT) bars act to self-center the SC-CBF after an earthquake. Laboratory results show that this system performs well under intense ground motions at the design basis earthquake (DBE) and the maximum considered earthquake (MCE) levels. The SC-CBF system was also subjected to the 1995 Kobe earthquake at 0.9 -scale and performed quite well under this ground motion. A performance-based seismic design procedure has been proposed for the SC-CBF system. This design procedure targets a performance condition of immediate occupancy (IO) under the DBE and collapse prevention (CP) under the MCE. The design procedure limits yielding of the PT bars under the DBE but permits significant yielding of the PT bars under the MCE. Frame members are designed using capacity design principles to remain essentially elastic under the DBE. Some member yielding is permitted under the MCE. This paper examines the effectiveness of the SC-CBF performance-based design procedure through several prototype designs.
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