Structures must have a reasonable seismic safety margin in order to ensure life-safety as well as to prevent structural collapse caused by earthquakes. On the other hand, the cost-efficiency and economy of structures are important and integral parts of structural engineering. The main aim of the current study is to propose an efficient methodology for designing cost-efficient multi-story special steel moment-resisting frames at predefined levels of seismic collapse safety. To achieve this purpose, a seismic collapse safety assessment technique is in-tegrated with performance-based design optimization in the present study. In order to illustrate the advantages of the proposed methodology, three design examples of 3-, 6-and 12-story special steel moment-resisting frames are presented. The numerical results show that by with a 25% increase in the optimal weight of the structures, their seismic collapse capacity increases by more than 50%.