Evaluation of Existing Reinforced Concrete Columns

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This project, in collaboration witha companion project by W. Holmes of Rutherford & Chekene (NSF Grant No. 9120214), is supported under the Phase 2 (second year) program of the Seismic Repair and Rehabilitation Initiative (NSF 90-23). Reinforced concrete frames constructed prior to the 1970's pose one of the greatest hazards for loss of life due to collapse during strong ground shaking. One of the key deficiencies of such structures is inadequate proportioning and detailing of columns. Examples of deficiencies include insufficient column strength relative to beam strength, light transverse reinforcement, and short lap splices. This research is to conduct an experimentally based study of the behavior of deficient columns and to develop methods for calculating strength and deformability of existing columns for use by structural engineers. The methods will be useful (a) for evaluation of existing structures and (b) for design of retrofitting systems that are intended to protect relatively brittle elements of the existing structure. The research includes a detailed review of existing data on performance of reinforced concrete columns, study of common details in existing structures, experiments on columns containing deficiencies representative of those found in existing construction, numerical modeling and analyses of results, and development of a practical set of rules for gaging the strength and deformability of reinforced concrete columns in existing structures. The research will be carried out jointly by researchers/engineers at the University of California at Berkeley and at Rutherford Chekene.