Debonding failure strength in RC beams strengthened with FRP for shear
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Abstract: The FRP-to-concrete interfacial debonding
is a fundamental key problem for the strengthening of RC structures
with externally bonded FRP sheets/plates. This paper presents the design
models and detail designs on the flexural or shear debonding of RC beams
strengthened with FRP sheets/plates, which is based on the latest experimental
and theoretical researches on the FRP-to-concrete interfacial constitutive
behavior, flexural and shear strengthening.
Keywords: FRP sheets/plates, strengthening, debonding, interface.
Numerical
modeling of FRP shear strengthened RC beams using compression field
theory
Proc. 3rd Int. Conf. for Composite in Civil Engineering
(CICE 2006), Miami, USA, 2006, 391-394.
Abstract: The modified compression field theory and an advanced bond-slip model are implemented in a general finite element analysis package to evaluate the shear behaviour of FRP strengthened reinforced concrete beams. The inclination angle of the critical shear crack is estimated and the debonding phenomenon is simulated. A close agreement is achieved between the predicted average FRP strains and those in a test beam reported in the literature. Further research is being conducted to simulate behaviour of FRP shear the interaction between the external FRP shear reinforcement and concrete.
keywords: Shear, FRP, strengthening, concrete, modified compression field theory (MCFT)
Debonding
Failure Strength in RC Beams Strengthened with FRP for Shear
Building
Structure, 36 (9), 2006, 31-36.
Abstract: Debonding failures always take place in reinforced concrete (RC) beams strengthened with externally bonded FRP against shear failure. Whilst the shear capacity may continue to increase after debonding for FRP wrapped beams, FRP debonding represents the ultimate failure state for most beams strengthened with U jacketing and side-bonding. This paper presents a review of existing studies on debonding failure. Using a rigorous local FRP-to-concrete bond-slip model, the stress distribution in FRP along the critical shear crack is then investigated by assuming several crack width distributions. A new design model is proposed. Compared with test data, the new model has similar accuracy with but is slightly conservative than Chen and Teng¡¯s model.
Key words: FRP, debonding, shear strengthening, reinforced concrete beam, shear strength
Numerical
Research On Shear Behaviors Of RC Beams Strengthened With U-Type FRP
Sheets
Engineering
Mechanics, 22(4).2005.155-162
Abstract:
The utilization of FRP in the shear strengthening for reinforced concrete
beams represents an effective way in upgrading the low loading capacity
of the beams due to the lack of web reinforcement. Based on the tests
data of seven beams, this paper presents analysis of FRP strengthened
RC beams using 3-D finite element model with the calculation performed
on ANSYS. The effects of various parameters on numerical results are
discussed with the bond strength bewteen FRP and concrete, shear transfer
coefficients for cracks finally determined. The numerical results shows
good agreement with the experimental results. To gain a better understanding
of the role FRP plays in the RC beam shear strengthing, further investigation
is conducted with respects to the distribution of strain in FRP under
each load level¡¢the FRP¡¯s contribution to the overall shear strength¡¢the
peeling-off process of FRP from the concrete¡¯s surface and the relationship
between the efficiency and the amount of FRP used in the shear strengthing.
Key
word: FRP; shear strengthening; finite element analysis; bond strength;
strain; peel-off process
Size
effect of shear contribution of externally bonded FRP U-jackets for
RC beams
Proc. International Symposium on Bond Behaviour of FRP
in Structures (BBFS 2005), Hong Kong, China, 2005. 371-380
ABSTRACT: It is well known that size effect exists in the shear strength of RC beams. Larger beams have a smaller nominal maximum shear strength. The size effect in RC beams shear strengthened with FRP has not been considered in existing predictive models. In these strengthened beams, the size effect may exist in the shear contributions of both RC beams and FRP. To better understand the shear strengthening and its corresponding size effect, a series of geometrically similar concrete beams strengthened with CFRP U-jackets were designed and tested in this study. The total shear strength of a strengthened RC beam is considered to consist of three components which are the shear contribution of the RC beam, and the direct and indirect shear contributions of the FRP. The direct shear contribution of FRP is obtained in this study with careful experimental measurements. An improved predictive model is proposed, which can obviously remove the size effect on direct FRP shear contribution. More studies are needed to quantify the indirect FRP shear contribution.
Theoretical
analysis of stress distributions in FRP side-bonded to RC beams for
shear strengthening
Proc. International Symposium on Bond Behaviour of FRP
in Structures (BBFS 2005), Hong Kong, China, 2005. 363-370.
ABSTRACT: Extensive research has been conducted on the strengthening of reinforced concrete (RC) beams with externally bonded fibre reinforced polymer (FRP) composites in the last decade. The FRP composites are usually installed following one of three common schemes: complete wrapping, U jacketing, and side bonding (bonding on their sides only). Experimental studies have shown that most side-bonded beams fail due to debonding of the FRP from the concrete. A key factor influencing the contribution of the FRP to the shear capacity of the beam is the stress (or strain) distribution in the FRP at the ultimate limit state. This paper presents a theoretical study of the stress distribution in the FRP along the critical shear crack at debonding failure of side-bonded beams for several assumed crack width variations, using a rigorous FRP-to-concrete bond-slip model. Numerical results show that Chen and Teng¡¯s (2001a, 2003a) simple assumption for the stress distribution in the FRP results in satisfactory predictions for the effective FRP stress in most cases. However, it can become unconservative for beams lightly reinforced in flexure but this is less relevant in practice because flexure rather than shear is the intended control failure mode.
ABSTRACT: Reinforced concrete (RC) beams may be strengthened for shear with externally bonded fibre reinforced polymer (FRP) composites through one of three common schemes: complete wrapping, U jacketing, and bonding on their sides only. The two main shear failure modes in such strengthened beams are FRP rupture and FRP debonding. In both failure modes, the stress (or strain) distribution in the FRP at the ultimate state is non-uniform and is a key factor influencing the contribution of the FRP to the shear capacity of the beam. This paper presents a theoretical study on the stress distribution in the FRP along the critical shear crack at debonding failure of U jacketed beams for several assumed crack width variations using a rigorous FRP-to-concrete bond-slip model. Numerical results show that Chen and Teng¡¯s [1, 2] simple assumption of stress distributions in the FRP results in satisfactory predictions of the shear strength.
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Comparison with other existing models |
