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SUMMARYThe damage observed after the Northridge Earthquake exposed a weakness of design and construction procedures and led to the development of performance-based guidelines for design of new steel frame structures. As part of Phase 2 of the FEMA=SAC project, this study focused on performance prediction of new steel special moment resisting frame buildings assumed to be built after the Northridge earthquake. A total of 26 post-Northridge buildings that represent typical steel SMRF buildings based on the new seismic code (1997 NEHRP) and pre-qualiÿed post-Northridge connections were designed. Then, the analytical building models considering the e ects of ductile connections, panel zone deformation and interior gravity frames were developed and subjected to sets of 20 SAC ground motions representing the 2=50 and 50=50 hazard levels. A new procedure that allows the design professional to determine the conÿdence level for achieving a given performance objective is presented. Using the drift demand and capacities, conÿdence levels that post-Northridge buildings will satisfy the collapse prevention and immediate occupancy performance level are calculated. All of the post-Northridge buildings exhibit a high conÿdence of performing well in future earthquakes.