Repair of reinforced concrete beam by adding external reinforcement

Abstract

The negligence in construction are usually due to error in replace or calculation of required reinforcement. The mistake known after construction and must be corrected as soon as possible. Some actions should be taken namely, add some pretension, augmented the beam size, use the FRP, and add some external reinforcement. Studies on rehabilitation and retrofitting are gaining importance due to the need for restoration of partially damaged structures due to wind load and earthquake. To prevent any disaster during the future earthquakes, the existing deficient buildings need to be retrofitted. The external tension reinforcement added when the flexural beam capacity inadequate, and the stirrups added when the shear beam capacity inadequate. The adding with external reinforcement also done after some tensile failure or cracks in the beam. In this case some damage of concrete must being consider in reducing stiffness and strength. The objective of this research is studied about the adding of external tensile reinforcement and stirrups after tensile failure and explore the influence of those action to the beam and then compared the strength, stiffness, ductility and crack pattern of beams before and after retrofit. The specimens were 12 original beam, and 12 retrofitted beam. The original beams have dimensions of 15 cm x 15 cm x 100cm, the tensile reinforcement were 46 and compression reinforcement 26. The stirrups were 6-200 along the beam. Retrofit strategies were adding bottom tensile reinforcement 26 and 36, and adding stirrups 6-60 in the shear span. The experiment shown the increase of beam ultimate load after retrofitting, but decrease the ductility and stiffness of the beam. The pattern of cracks also changed between original and retrofitted beam.