Abstract
Carbon fiber-reinforced plastic (CFRP) reinforced concrete beams can fail due to interface debonding, due to the high tensile strength of such rebars. A set of 16 concrete beams reinforced with different amounts of CFRP reinforcement was subject to static three-point bending. The beam dimensions and CFRP reinforcements used were selected to demonstrate a transition from compression failure to bond failure with decreasing reinforcement ratio. It is shown that accurate bond strength data to predict such failures can be obtained from a “hinged-beam” test configuration, rather than the conventional direct “pull-out” tests. Deflection under service loads can also be predicted more accurately using a proposed equation that includes the reinforcement ratio and the elastic modulus of the reinforcement.
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Abbreviations
- f'c :
-
concrete strength in compression
- E f :
-
E lb =E FRP =modulus of elasticity of the FRP
- ρ f :
-
ratio of tension reinforcement=A f /bd
- A FRP :
-
A f =area of the FRP tension reinforcement
- b :
-
width of the member
- d :
-
distance from extreme compression fiber to centroid of tension reinforcement
- α1 :
-
ratio of the depth of the equivalent rectangular stress block to the depth to the neutral axis at ε cu
- f fd :
-
0.65f fu
- c b :
-
ε cu d/(ε cu +ε fd )
- ε cu :
-
maximum concrete strain in compression
- ε fd :
-
rebar strain=f fd /E f
- d b :
-
diameter of the rebar
- A b :
-
cross-sectional area of the rebar
- C :
-
constant=πd b /E lb A b
- x :
-
distance along the bar starting at the free end of the beam
- ε b (x):
-
rebar strain variation along the distancex
- N(x) :
-
normal force along the bar
- k :
-
constant that multiplied by the effective depth of the section gives the neutral axis position from the compression
- fiber:
-
\(\sqrt {(\rho n)^2 + 2(\rho n) - } (\rho n)\)
- I cr :
-
cracked moment of inertia of a cross section=(kd) 3 (b)/3+nA FRP (d−kd) 2
- E c :
-
modulus of elasticity of the concrete
- n :
-
modulus ratio=E FRP /E c
- I g :
-
gross moment of inertia
- f r :
-
modulus of rupture of the concrete
- M cr :
-
cracking moment=f r (I tr )/y t
- I tr :
-
moment of inertia of the transformed section
- y t :
-
distance from centroidal axis to the extreme fiber in tension
- I e :
-
effective moment of inertia
- M a :
-
maximum moment in a member at the stage for which deflection is computed
- α:
-
0.84
- β:
-
7.0
- γ:
-
reduction factor=E FRP /E s
- ŋ:
-
100 π−0.2
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Maji, A., Orozco, A.L. Prediction of bond failure and deflection of carbon fiber-reinforced plastic reinforced concrete beams. Experimental Mechanics 45, 35–41 (2005). https://doi.org/10.1007/BF02428988
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DOI: https://doi.org/10.1007/BF02428988