Abstract
This paper investigates the strengthening of reinforced concrete (RC) beams for its torsional behavior using aramid fiber strips. Most of the time aramid fiber is used as an externally bonded reinforcement to increase flexural and shear strength of RC beams. An attempt is made to use it for improving torsional moment carrying capacity of RC beam. Torsional failure mostly occurs in earthquake prone areas subjected to rapid failure. Brittle failure of structures occurs due to torsional moment. Different patterns of aramid fiber strips are selected to wrap around RC beams and torsional behavior of these strengthened beams is studied. RC beam of M30 grade of concrete is strengthened with aramid fiber strips and tested for torsional failure using lever arms subjected to torque. The beam size is 150 mm × 300 mm and of 1.3 m in length, designed as per IS456-2000. A total of 21 numbers of reinforced concrete rectangular beams were cast for the experimental study. Three are taken as controlled beams with normal reinforcement, 3 beams are designed with torsional reinforcement and other 15 beams with normal reinforcement have grouped in five sets. These five sets are strengthened using aramid fiber strips of 150 mm width with variable spacing of 100, 125, 150, 175 and 200 mm, respectively. The effect of different configuration of aramid fiber on torsional moment carrying capacity, angle of twist and failure mode of the beams is studied.
Highlights
The civil engineering structures constructed around 50 years before are reaching a critical stage, undergo deterioration and reduced functionality
Three beams are designed with torsional reinforcement and other 15 beams having normal reinforcement are strengthened using aramid fiber strips of five different patterns
The angle of twist of each beam is compared with the angle of twist of controlled beam
Summary
The civil engineering structures constructed around 50 years before are reaching a critical stage, undergo deterioration and reduced functionality. Most of the research is done on RC beams strengthened with FRP subjected to shear and flexure Many structural members such as curved girders, space frames, eccentrically loaded beams, spandrel beams in buildings, and spiral staircases are subjected to torsional moment. In this research an attempt is made to strengthen the reinforced concrete beam using aramid fiber. Three beams are designed with torsional reinforcement and other 15 beams having normal reinforcement are strengthened using aramid fiber strips of five different patterns. As the FRP material is to be wrapped around structural members for external strengthening, surface characteristics of concrete are very important to furnish proper bond in the contact area. Epoxy resin and hardener are mixed together with the ratio of 100:30, and applied to the aramid fiber and on the surface of the beam. If any, is removed in between fabric and beam surface
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