EVALUATION OF REINFORCED CONCRETE BEAMS STRENGTHENED EXTERNALLY BY A TWO-LAYER OF CARBON FIBER REINFORCED POLYMER
Keywords:
beam, concrete, ductility, deflection, load, flexure, Two-layer, CFRPAbstract
This paper investigates reinforced concrete (RC) beams strengthened externally with a two-layer carbon fiber reinforced polymer (CFRP). The CFRP fabric strips were cut to the required size and were bonded to the RC beam by Sikadur(R)-31 epoxy resin. After the epoxy glue Sikadur(R)-31 was mixed, it was scraped into the concrete surface to the desired thickness. Four (4) out of nine (9) beam samples were strengthened with two-layer of 200 g/m2 and another set of four beams was strengthened with two-layer of 300 g/m2 CFRP fabric of 100 mm width and 1100 mm length with a 2, 4, 6, and 8 mm bond thicknesses on the first layer and another 2 mm
bond thickness on the second layer applied at the tension face as a model of the prototype. The remaining beam was not strengthened and was taken as a control beam. Before loading, the structural epoxy resin was cured for at least seven days at room temperature. The beams were tested on a 20-ton (196.3 kN) loading frame to examine the load-carrying capacity and load-deformation response. One-third point load application was used. The study showed the possibility of using two-layer epoxy-bonded CFRP fabrics to enhance the load resistance in the flexure and shear of RC beams. However, doubling the CFRP layer does not result in further increments in load resistance. Carbon fiber-reinforced polymer is useful in upgrading existing RC beams externally. However, it reduces the capacity of the beam to resist deformation under external load. The serviceability of the reinforced concrete beam member is usually evaluated through deformation and crack width. The deformation of an RC member strengthened with two-layer epoxy-bonded CFRP fabric was observed to be higher at failure relative to a concrete beam without epoxy-bonded CFRP fabric. The
two-layer bonded CFRP fabric increased the bending strength by up to 55% as long as the suitable strengthening configurations and the appropriate bond thickness were used.
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