Evaluation of bond stress-slip models for FRP reinforcing bars in concrete

Outline

• Abstract
• Keywords
• 1. Introduction
• 2. Bond Stress-Slip Models of Frp Rebars in Concrete
• 2.1. Malvar’s Model
• 2.2. Bpe Model
• 2.3. Bpe Modified Model
• 2.4. Cmr Model and Tighiouart Et Al.’s Model
• 3. Bond Stress-Slip Models of Steel Rebars in Concrete
• 3.1. Harajli Et Al.’s Model
• 3.2. Haskett Et Al.’s Model
• 3.3. Soroushian and Choi’s Model
• 3.4. Yankelevsky’s Model
• 3.5. Trilinear Bond Stress-Slip Model
• 4. Evaluation of Bond Stress-Slip Models
• 4.1. Finite Element Model
• 4.2. Finite Element Analysis of a Gfrp-Reinforced Concrete Beam
• 4.2.1. Finite Element Analysis of a Gfrp-Reinforced Concrete Beam Using the Bpe Modified Model
• 4.2.2. Finite Element Analysis of a Gfrp-Reinforced Concrete Beam Using the Bpe Model
• 4.2.3. Finite Element Analysis of a Gfrp-Reinforced Concrete Beam Using the Cmr Model
• 4.2.4. Finite Element Analysis of a Gfrp-Reinforced Concrete Beam Using the Harajli Et Al.’s Model
• 4.2.5. Finite Element Analysis of a Gfrp-Reinforced Concrete Beam Using the Haskett Et Al.’s Model
• 4.3. Finite Element Analysis of a Cfrp-Reinforced Concrete Beam
• 4.3.1. Finite Element Analysis of a Cfrp-Reinforced Concrete Beam Using the Bpe Modified Model
• 4.3.2. Finite Element Analysis of a Cfrp-Reinforced Concrete Beam Using the Bpe Model
• 4.3.3. Finite Element Analysis of a Cfrp-Reinforced Concrete Beam Using the Cmr Model
• 4.3.4. Finite Element Analysis of a Cfrp-Reinforced Concrete Beam Using the Harajli Et Al.’s Model
• 4.3.5. Finite Element Analysis of a Cfrp-Reinforced Concrete Beam Using the Haskett Et Al.’s Model
• 5. Parametric Study
• 6. Conclusions
• References

Conclusions

In order to generate more accurate results for structural analysis of FRP-reinforced concrete structures, it is of great importance to include bond-slip effect of FRP rebars in the finite element model. However, very few mature bond stress-slip models for FRP rebars have been reported so far. In this paper, several currently available bond stress-slip models for steel and FRP rebars are reviewed, and three most promising models for FRP rebars and two models for steel rebars are evaluated by building them into a newly-developed finite element model for analysis of FRP-reinforced concrete beams. Although the Malvar’s Model gives a complete description of the bond stress-slip relation curve of FRP rebars, it is assessed to be less comprehensive and less reliable. The Tighiouart et al.’s Model describes the ascending part of the bond stress slip curve, but it is found to have mistake in its expression. By comparing the numerical results, the BPE Model calibrated by Rossetti et al. [24] has found to be not applicable to be implemented in numerical analysis. The BPE Model calibrated by Cosenza et al. [14] can produce much better results than the one calibrated by Rossetti et al. [24] when being used to model the bond-slip behaviour of FRP rebars in numerical model, however, the results are not consistent for different cases. In addition, good predictions can only be generated at the beginning of loading by using the CMR Model, and the predicted bearing capacity is much lower than the test data. The predictions given by the finite element analysis using bond stress-slip models for steel rebars, i.e. Harajli et al.’s Model and Haskett et al.’s Model, are not accurate enough, and the discrepancies develop with the increase in load. From this study, the BPE Modified Model is demonstrated to be the best bond stress-slip model for FRP rebars among the others. In the numerical analyses of GFRP and CFRP-reinforced concrete beams, the finite element model with the BPE Modified Model gives very good predictions for both the global structural behaviour of concrete beams and the local strain on the reinforcing bars, and the calculated results are more accurate and consistent than the others. However, the BPE Modified Model is not without its deficiencies, such as the negligence of the effects of rebar diameter and fibre type in the model, therefore further work on the bond strength and bond stress-slip constitutive relationship of FRP rebars is still in demand, especially the effects of various factors on the bond behaviour should be taken into account.

Parametric study is also carried out based on the BPE Modified Model to investigate the effect of rebar surface on the structural behaviour of FRP-reinforced concrete structures. It is found that the type of rebar surface has a significant influence on bond strength and structural behaviour. The grain-covered surface provides the best bond between the FRP rebars and concrete, the smooth surface the worst, and FRP rebars with ribbed and braided surfaces perform similarly.