This paper presents the test results of an experimental study that investigates the
behavior of reinforced concrete (RC) beams strengthened or repaired in flexure by
adding thin lower concrete layer reinforced mainly by Fiber Reinforced polymers
(FRP) bars. A total of seventeen RC beams were constructed and tested under fourpoint
loading. One of these beams was un-strengthened and considered as a reference
beam. Eight beams were strengthened in flexure, and the other eight beams were
loading up to 70% from the ultimate load of reference beam and then repaired using
the same methods provided to the strengthened beams. Five test parameters were
considered in this research; status of beam (strengthened or repaired), type of
reinforcement used (glass FPR, carbon FPR or steel), amount of reinforcing FRP
bars used (2 bars or 4 bars), type of the strengthening technique (reinforcing bars
installed in the adding concrete layer or FRP sheets externally bonded to the soffit of
the adding concrete layer) and type of connection between the adding lower concrete
layer and the original beam (installing dowels bars or not). The test results included
ultimate load, cracking load, the corresponding deflection, the failure modes and
calculated relative ductility and flexure stiffness at un-cracked and cracked stages.
The percentage enhancement in the flexural capacity of the tested beams ranged from
32% to 106% compared with the reference beam. Using FRP bars showed greater
ultimate load and more ductile behavior than using externally FRP sheets. Many
failure modes were observed during testing; FRP rupture, FRP debonding or partial
debonding between the adding concrete layer and the original beam depending on the
method of strengthening or repairing had been applied to the tested beams. The
experimental ultimate strength for all strengthened and repaired beams were
compared with the design provisions provided by ACI 440-2R-08, which showed
reasonable and lightly conservative predictions for all strengthened and repaired
beams |
