This project is supported under Phase 2 of the Seismic Repair and Rehabilitation Initiative (NSF 90- 23). Reinforced concrete frame structures constructed in the U.S. during the 1950's and 1960's often include non-ductile details associated with poor seismic performance. The behavior of these details has been studied experimentally. This project addresses strategies for improving the seismic performance of these structures. The objectives of the research are: (1) to outline strategies for retrofit of non-ductile concrete frame structures, (2) to investigate retrofit strategies based on improving the strength and ductility of critical frame details and regions, (3) to provide a methodology for evaluating retrofit frames, (4) to use the methodology to estimate the levels of strength and ductility needed for critical regions, and (5) to recommend guidelines for strength and ductility improvement. A series of non-ductile concrete frame structures will be analyzed and retrofit strategies will be formulated. Analytical models will be calibrated with recent experimental results. Retrofit frames will be analyzed and retrofit strategies will be evaluated. Guidelines for appropriate levels of critical region strength and ductility will be developed, and a methodology for assessing retrofit strategies will be provided. The guidelines and methodology will assist other researchers in developing retrofit techniques, and will assist practicing engineers in the retrofit of existing structures. The project will include interactions with other researchers and practicing engineers in the seismic design of buildings.
