This project is supported under NSF Announcement NO. 90-23, "Repair and Rehabilitation Research for Seismic Resistance of Structures." The need to strengthen existing buildings with inadequate seismic resistance is an urgent problem in the field of earthquake engineering. A major class of existing structures identified as posing one of the greatest seismic hazards are nonductile concrete frames. A number of strengthening techniques for concrete frames include addition of structural walls, addition of steel bracing, and enlarging of columns and beams using reinforced concrete jackets. An alternative approach to concrete jackets is the use of external steel jackets and plates attached to the existing members. Steel jackets may offer significant advantages of reduced labor, reduced cost, and reduced disruption to existing facilities, as compare to the use of concrete jackets. The proposed research program will investigate critical issues associated with the use of external steel jackets and plates for strengthening nonductile concrete frames. The project consists of a number of interrelated tests, divided into three major phases: I - behavior of steel-to-concrete connections; II - behavior of individual members strengthened with steel jackets; and III - behavior of beam-column subassemblages strengthened with steel jackets. The overall objective of the project is to develop design guidelines for the effective implementation of steel jackets as a strengthening and repair technique. This project is one part of a collaborative research activity involving an academic institution and two professional engineering offices in a common effort to implement research results into practice.
