ABSTRACT
A retrofitting trial design analysis of a thirteen-story steel moment frame building damaged by the 1994 Northridge earthquake is presented. The structural rehabilitation hypothesis consisted of introducing bracing members equipped with fluid viscous dampers in each one of the four perimeter frames constituting the lateral load resisting system of the building. A special energy-based design criterion developed within the context of a nonlinear dynamic procedure approach, previously proposed and utilized for a new construction project, was applied to this case study. The design analysis, complying with FEMA 273 – NEHRP Guidelines for the Seismic Rehabilitation of Buildings, was aimed at obtaining Immediate Occupancy Performance Level for the building. Feasible dimensions and costs came out for the dampers ensuring attainment of this notably demanding objective. The substantially upgraded seismic performance of the structural system was confirmed by the undamaged response derived from a more severe register of Northridge event than the one actually recorded at the basement of the building.
