Skip to main content
SpringerLink
Log in

An Experimental Study on the Debonding of Steel and CFRP Strips Externally Bonded to Concrete in the Presence of Embedded Shear Connectors

  • Research Article - Civil Engineering
  • Published:
Arabian Journal for Science and Engineering Aims and scope Submit manuscript

Abstract

The problem of debonding failure is a fundamental issue in concrete structures that are externally strengthened with adhesively glued plates. Many standards and studies recommend using single-lap pull-out tests to measure the ultimate force that causes debonding failure. The pull-out test also allows defining and calibrating interface bond-slip relationships between concrete and the bonded plates to obtain the maximum interfacial bond strength. The aim of this research was to enhance bond strength in the presence of embedded shear connectors, which were fabricated at concrete–adhesive interface level to delay debonding of the externally bonded strips from the concrete surface. A new rational model was also proposed to predict the bond strength of adhesively glued plates-to-concrete joints in the presence of connectors. In the experimental programme, 60 concrete prisms with adhesive and steel bar connectors were fabricated. The specimens were divided into two main series of concrete prisms bonded with steel plates and CFRP strips using the new connectors. Different diameters of connectors were used with and without adhesive on the surfaces of concrete prisms to bond the strips for investigating the capacity of the new embedded connectors. The experimental results showed that the interfacial bond strength increased remarkably when these connectors were used. Moreover, it was found that increasing the connector’s diameter has a great effect on increasing the bond strength and uniformly distributes the interfacial shear stresses, leading to the minimisation of premature debonding failure of bonded plates. The results exhibited that the steel connectors are more effective at increasing the shear bond strength for all specimens adhesively glued with both CFRP strips and steel plates. Finally, the proposed bond strength model was satisfactorily verified through the experimental investigations.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

Abbreviations

b c :

Width of concrete prism

b p, b w :

Width of bonded plate

R :

Regression Factor

κs :

Fracture energy coefficient

E a :

Young’s modulus of adhesive

E c :

Young’s modulus of concrete

E p :

Young’s modulus of bonded plate

\({f^{\prime}_{\rm c}}\) :

Concrete cylinder compressive strength

f ctm :

Concrete surface tensile strength

f ca :

Compressive strength of adhesive

f a :

Tensile strength of adhesive

f t :

Splitting tensile strength of concrete

G f :

Fracture energy

G a :

Shear modulus of adhesive

\({\beta_{\rm L}, \beta_{\rm w}}\) :

Geometrical factors

L, L b :

Actual bond length

L e :

Effective bond length

P u :

Ultimate bond strength

t c :

Thickness of concrete prism

t p :

Thickness of bonded plate

\({\delta}\) :

Displacement

\({\delta _{o}\delta _1}\) :

Initial and final displacements

v :

Poisson’s ratio

\({\tau}\) :

Shear stress between concrete and bonded plate

\({\tau _{\rm u}}\) :

Ultimate shear stress

\({\tau _{\rm db}}\) :

Debonding interfacial shear stress

\({\tau _{\rm Conn.}}\) :

Shear strength provided by connectors

F A.Conn. :

Shear strength provided by adhesive connectors

F S.Conn. :

Shear strength provided by steel connectors

F B :

Bearing strength provided by steel connectors

\({\sigma _{\rm db}}\) :

Debonding stress

\({\sigma _{\rm eff}}\) :

Effective longitudinal stress in the bonded plate

\({\varepsilon _{\rm eff}}\) :

Effective longitudinal strain in plate to prevent debonding

\({\varepsilon _{\rm db}}\) :

Debonding strain

A p :

Cross-sectional area of the bonded plate

A b :

Actual bonded area

n :

Number of connectors

\({\alpha_{\rm t}}\) :

Ratio of plate to concrete’s axial rigidity

References

  1. Kalfat R., Al-Mahaidi R., Smith S.: Anchorage devices used to improve the performance of reinforced concrete beams retrofitted with FRP composites: State-of-the-Art Review. J. Compos. Constr. 17(1), 14–33 (2013)

    Article  Google Scholar 

  2. Kaya M., Kankal Z.Ç.: Effect of anchorage number on behavior of reinforced concrete beams strengthened with glass fiber plates. Int. J. Concr. Struct. Mater. 9(4), 415–425 (2015)

    Article  Google Scholar 

  3. Grelle S.V., Sneed L.H.: Review of anchorage systems for externally bonded FRP laminates. Int. J. Concr. Struct. Mater. 7(1), 17–33 (2013)

    Article  Google Scholar 

  4. ACI 440.2R-08 (2008) Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures. American Concrete Institute, Farmington Hills, Mich.

  5. Canadian Standards Association (CSA). (2012). “Design and construction of building components with fibre-reinforced polymers”. CSA S806-12, CSA, Rexdale, Ontario, Canada.

  6. Japan Society of Civil Engineers (JSCE), (2001). Recommendations for upgrading of concrete structures with use of continuous fiber sheets. Concrete Engineering Series 41, Japan Society of Civil Engineers, Tokyo, Japan.

  7. Chen J.F., Teng J.G.: Anchorage strength models for FRP and steel plates bonded to concrete. J. Struct. Eng. ASCE 127(7), 784–791 (2001)

    Article  Google Scholar 

  8. Smith S.T., Teng J.G.: FRP-strengthened RC beams. I: review of debonding strength models. Eng. Struct. 24(4), 385–395 (2002)

    Article  Google Scholar 

  9. Yuan, H.; Teng, J.G.; Seracino, R.; Wu, Z.S.; Yao, J.: Full-range behavior of FRP-to-concrete bonded joints. Eng. Struct. 26(5), 553–64 (2004)

  10. Yao J., Teng J.G., Chen J.F.: Experimental study on FRP-to-concrete bonded joints. Compos. Part B Eng. 36(2), 99–113 (2005)

    Article  Google Scholar 

  11. Teng J.G., Yao J.: Plate end debonding in FRP-plated RC beams–II: Strength model. Eng. Struct. 29(10), 2472–2486 (2007)

    Article  Google Scholar 

  12. Ceroni F.: Experimental performances of RC beams strengthened with FRP materials. Constr. Build. Mater. 24(9), 1547–1559 (2010)

    Article  Google Scholar 

  13. Ashraful Alam M., Jumaat M.Z., Mustapha K.N.: Effective method of repairing RC beam using externally bonded steel plate. Appl. Mech. Mater. 567, 399–404 (2014)

    Article  Google Scholar 

  14. Bank L.C., Arora D.: Analysis of RC beams strengthened with mechanically fastened FRP (MF-FRP) strips. Compos. Struct. 79(2), 180–191 (2007)

    Article  Google Scholar 

  15. Ceroni F., Pecce M., Matthys S., Taerwe L.: Debonding strength and anchorage devices for reinforced concrete elements strengthened with FRP sheets. Compos. Part B Eng. 39(3), 429–441 (2008)

    Article  Google Scholar 

  16. Chaallal O., Mofidi A., Benmokrane B., Neale K.: Embedded through-section FRP rod method for shear strengthening of RC beams: performance and comparison with existing techniques. J. Compos. Constr. 15(3), 374–383 (2010)

    Article  Google Scholar 

  17. Mofidi A., Chaallal O.: Shear strengthening of RC beams with EB FRP: influencing factors and conceptual debonding model. J. Compos. Constr. 14(5), 62–74 (2011)

    Article  Google Scholar 

  18. Kim S.J., Smith S.T.: Behaviour of handmade FRP anchors under tensile load in uncracked concrete. Adv. Struct. Eng. 12(6), 845–865 (2009)

    Article  Google Scholar 

  19. Kim, S. J., and Smith, S. T. (2009b). Shear strength and behaviour of FRP spike anchors in cracked concrete. Proceedings of 9th International Symposium on Fiber Reinforced Polymer Reinforcement for Concrete Structures, FRPRCS-9, Thomas Telford Publishing, London.

  20. Kim S.J., Smith S.T.: Pullout strength models for FRP anchors in uncracked concrete. J. Compos. Constr. 14(4), 406–414 (2010)

    Article  Google Scholar 

  21. Alam M.A., Jumaat M.Z.: Prevention of debonding failure of intermediate anchor to eliminate premature shear failure of flexurally strengthened reinforced concrete beams. Arabian J. Sci. Eng. 40(8), 2219–2232 (2015)

    Article  Google Scholar 

  22. Smith S.T., Teng J.G.: FRP-strengthened RC structures–II: assessment of debonding strength models. Eng. Struct. 24(4), 397–417 (2002)

    Article  Google Scholar 

  23. Teng J.G., Zhang J.W., Smith S.T.: Interfacial stresses in reinforced concrete beams bonded with a soffit plate: a finite element study. Constr. Build. Mater. 16(1), 1–14 (2002)

    Article  Google Scholar 

  24. Chen J.F., Teng J.G.: Shear capacity of FRP-strengthened RC beams: FRP debonding. Constr. Build. Mater. 17(1), 27–41 (2003)

    Article  Google Scholar 

  25. Pellegrino C., Tinazzi D., Modena C.: Experimental study on bond behavior between concrete and FRP reinforcement. J. Compos. Constr. 12(2), 180–189 (2008)

    Article  Google Scholar 

  26. Chajes M.J., Finch William.W., Januszka T.F., Thomson T.A.: Bond and force transfer of composite material plates bonded to concrete. ACI Struct. J. 93(2), 208–217 (1996)

    Google Scholar 

  27. Khalifa A., Gold W.J., Nanni A., MI A.A.: Contribution of externally bonded FRP to shear capacity of RC flexural members. J. Compos. Constr. 2(4), 195–202 (1998)

    Article  Google Scholar 

  28. Dai J., Ueda T., Sato Y.: Development of the nonlinear bond stress–slip model of fiber reinforced plastics sheet–concrete interfaces with a simple method. J. Compos. Constr. 9(1), 52–62 (2005)

    Article  Google Scholar 

  29. Täljsten B.: Strengthening of concrete prisms using the plate-bonding technique. Int. J. Fract. 82(3), 253–266 (1996)

    Article  Google Scholar 

  30. CNR. (2004). Guidelines for design, execution, and control of strengthening interventions by means of fiber-reinforced composites. DT200, National Research Council, Italy.

  31. BSI (2004) BS EN 1992-1-1 Eurocode 2: Design of Concrete Structures Part 1-1: General Rules and Rules for Buildings. British Standards Institution, London, UK.

Download references

Author information

Authors and Affiliations

  1. Department of Civil Engineering, College of Engineering, Universiti Tenaga Nasional, JalanIkram-Uniten, Kajang, Selangor, Malaysia

    Md Ashraful Alam, Ali Sami Alshaikhly & Kamal Nasharuddin Mustapha

Authors
  1. Md Ashraful Alam
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Ali Sami Alshaikhly
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Kamal Nasharuddin Mustapha
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Ali Sami Alshaikhly.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Alam, M.A., Alshaikhly, A.S. & Mustapha, K.N. An Experimental Study on the Debonding of Steel and CFRP Strips Externally Bonded to Concrete in the Presence of Embedded Shear Connectors. Arab J Sci Eng 41, 4171–4186 (2016). https://doi.org/10.1007/s13369-016-2123-5

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s13369-016-2123-5

Keywords

Search

Navigation