Experimental Strengthening of Damaged and Un-Damaged RC Frames with Ultra-FRC Composite Layers

FRC concretes with high strength are practical material for strengthening existing particularly damaged concrete structures and able to dissipate seismic energy. The main purpose of this paper was to using high strength-FRC concrete for strengthening the damaged and undamaged frames. The five experimental specimens were loaded laterally and vertical gravity loads, simultaneously. The first specimen was a reference without strengthening, but the second same specimen was strengthened. The other three specimens were initially were loaded up to 55, 75, and 100% of the maximum capacity of the reference specimen and prepared as damaged specimens. The damaged specimens were laterally and vertically loaded. The test results showed that ductility of the undamaged strengthened frame was 2.2 times that of the reference specimen, while these amounts for three strengthened specimens (55, 75, and 100%) were up to 110, 60, 15 increase compared to the reference.  The maximum lateral capacity of second undamaged, third fourth, and fifth damaged specimens were 38 and 35, 16, 9% more than that of reference; while the significant increase of energy absorption from 1.28 to 2.37 times reference was observed.