Older reinforced concrete frame structure constructed in seismic areas of the United States are usually non-ductile and are thus identified as hazardous. Laboratory studies have shown that the use of "ordinary" Fiber Reinforced Concrete (FRC) in a new construction has substantially improved seismic response, but conventional seismic retrofit techniques have not yet taken advantage of FRCs or High Performance FRCs (HPFRCs). The advantage of FRCs is a significant increase in ductility over that of conventional reinforced concrete. The advantage of HPFRC is that, when loaded beyond the elastic limit, these materials exhibit a significant improvement in the ability to undergo further increase in stress and strain before failure. This increase in tensile strength and ductility leads to an enormous increase in ability of the structural frame to dissipate energy-a feature particularly desirable for earthquake-resistance design. ***The goals of this research project herein is to develop an innovative technique for seismic retrofit of nonductile reinforced concrete frames using recently developed HPFRCs which exhibit significant increase in the composite strain and stress capacity in the inelastic range. Use of this material can solve the following common problems of reinforced concrete frames: (1) Inadequate anchorage of the discontinuous bottom reinforcement in beams, (2) inadequate confinement of the column lap splices, and (3) inadequate confinement of the joint. The research is expected to open up a new area for seismic repair and rehabilitation of non-ductile structures by using newly developed HPFRC composites. The project is supported under NSF Initiative "Repair and Rehabilitation Research for Seismic Resistance of Structures."***
