Seismic behavior of shear-critical reinforced concrete frame: Experimental investigation

Many reinforced concrete structures that were built approximately 40 years ago or earlier and some built much more recently, were done so without adequate consideration for shear-critical behavior under seismic conditions. Such buildings are of great concern because, in the event of an earthquake, they may fail in a brittle. and catastrophic manner. Unlike with moment-critical structures the behavior of structures that are shear-critical under seismic load conditions has not been well studied. An experimental investigation was carried out to examine the behavior of a shear-critical reinforced concrete frame under seismic loading. A single-span, two-story, reinforced concrete frame with shear-critical beams was constructed and tested in a lateral reverse cyclic manner until severe shear damage took place in the beams. The beams were then repaired with carbon fiber reinforced polymer (CFRP), arid the frame was retested. The damage mode in the beams after repair changed from shear to flexure-controlled. In addition, substantial improvements were observed in overall peak lateral load, ductility, maximum displacement, and energy dissipation. The experimental findings concluded that CFRP wrap can be a simple and effective means of repair of shear-deficient frames, and that the CFRP strain, limitations proposed by ISIS Canada are conservative.