Behavior of RC Beams Strengthened with Externally Post-Tensioning CFRP Strips


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Title: Behavior of RC Beams Strengthened with Externally Post-Tensioning CFRP Strips

Author(s): K.-S. Choi, Y.-C. You, Y.-H. Park, J.-S. Park, and K.-H. Kim

Publication: Special Publication

Volume: 230


Appears on pages(s): 515-528

Keywords: bonded; CFRP strips; debonding failure; external post-tensioning; strengthening; unbonded

Date: 10/1/2005

Experimental study has been performed in order to investigate the behaviorof RC beams strengthened with externally post-tensioning CFRP (Carbon FiberReinforced Polymer) strips. A total of 11 specimens have been manufactured of whichspecimens strengthened with bonded or unbonded CFRP strips considering the level ofpost-tensioning as experimental variable, and a specimen with simply bonded CFRPstrips. The following phenomena have been observed through the experimental results.The specimen with simply bonded CFRP strips failed below 50% of its tensile strengthdue to premature debonding. On the other hand, all the specimens strengthened withpost-tensioning CFRP strips showed sufficient strengthening performance up to theultimate rupture load of the CFRP strips. Also, it was observed that the cracking loadsand yield loads of the strengthened beams were increased proportionally to the post-tensioning level, but the ultimate loads were nearly equal regardless of the post-tensioning level and bonded or unbonded system. In addition, the yield loads andcracking loads of the beams with bonded post-tensioning systems were increasedabout 20% compared with those of the unbonded post-tensioning systems. However,the beams strengthened with unbonded post-tensioning CFRP strips showed ductilebehaviour with large deflections resulting from the reduced member stiffness.