Concrete Beams Strengthened with Prestressed Near Surface Mounted CFRP
Publication: Journal of Composites for Construction
Volume 10, Issue 1
Abstract
Retrofitting concrete structures with fiber reinforced polymer (FRP) has today grown to be a widely used method throughout most parts of the world. The main reason for this is that it is possible to obtain a good strengthening effect with a relatively small work effort. It is also possible to carry out strengthening work without changing the appearance or dimensions of the structure. Nevertheless, when strengthening a structure with external FRP, it is often not possible to make full use of the FRP. The reason for this depends mainly on the fact that a strain distribution exists over the section due to dead load or other loads that cannot be removed during strengthening. This implies that steel yielding in the reinforcement may already be occurring in the service limit state or that compressive failure in the concrete is occurring. By prestressing, a higher utilization of the FRP material is made possible. It is extremely important to ensure that, if external prestressing is used, the force is properly transferred to the structure. Most of the research conducted with prestressing carbon fiber reinforced polymer (CFRP) for strengthening has been on surface bonded laminates. However, this paper presents research on prestressed CFRP quadratic rods bonded in sawed grooves in the concrete cover. This method has proven to be an advantageous means of bonding CFRP to concrete, and in comparison to surface bonded laminates, the shear and normal stress between the CFRP and the concrete are more efficiently transferred to the structure. In the presented test, no mechanical device has been used to maintain the prestress during testing, which means that the adhesive must transfer all shear stresses to the concrete. Fifteen beams with a length of have been tested. The tests show that the prestressed beams exhibited a higher first-crack load as well as a higher steel-yielding load as compared to nonprestressed strengthened beams. The ultimate load at failure was also higher, as compared to nonprestressed beams, but in relation not as large as for the cracking and yielding. In addition, the beams strengthened with prestressed FRP had a smaller midpoint deflection. All strengthened beams failed due to fiber rupture of the FRP.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The writers acknowledge the financial support that has been provided by SKANSKA AB, Sto Scandinavia AB, and The Development Fund of the Swedish Construction Industry (SBUF). Also, Håkan Johansson, Lars Åström, and Georg Danielsson at Testlab, Luleå University of Technology, are acknowledged for their help and support.
References
Asplund, S. O. (1949). “Strengthening bridge slabs with grouted reinforcement.” J. Am. Concr. Inst., 20(6), 397–406.
Carolin, A. (2003). “Carbon fiber reinforced polymers for strengthening of structural elements.” PhD thesis, Luleå Univ. of Technology, Luleå, Sweden.
De Lorenzis, L., Nanni, A., and La Tegola, A. (2000). “Flexural and shear strengthening of reinforced concrete structures with near surface mounted FRP rods.” Proc., 3rd Int. Conf. on Advanced Composite Materials in Bridges and Structures, J. L. Humar and A. G. Razaqpur, eds., Canadian Society for Civil Engineering, Ottawa, 521–528.
El-Hacha, R., Gren, M., and Wight, G. (2001a). “Concrete beams post-strengthened with prestressed carbon fibre reinforced polymer sheets.” Proc., Structural Faults and Repair Conf., Commonwealth Institute, London.
El-Hacha, R., Gren, M., and Wight, G. (2003). “Innovative system for prestressing fiber reinforced polymer sheets.” ACI Struct. J., 100(3), 305–313.
El-Hacha, R., Wight, G., and Green, M. (2001b). “Long-term behavior of concrete beams strengthened with prestressed CFRP sheets at room and low temperatures.” Proc., Conf. on Concrete Under Severe Conditions—Environment and Loading, N. Banthia, K. Sakai, and O. E. Gjörv, eds., Univ. of British Columbia, Vancouver, Canada, 1817–1826.
Garden, H. N., and Hollaway, L. C. (1998). “An experimental study of the failure modes of reinforced concrete beams strengthened with prestressed carbon composite plates.” Composites, Part B, 29(4), 411–424.
Hassan, T., and Rizkalla, S. (2001). “Strengthening of bridge slabs with FRP systems.” Proc., Structural Faults & Repair Conf., Commonwealth Institute, London.
Meier, U. (1995). “Strengthening of structures using carbon fibre/epoxy composites.” Constr. Build. Mater., 9(6), 341–351.
Meier, U. (2001). “Poststrengthening with CFRP strips: of practical experience.” Proc., ACUN-3 Technology Convergence in Composite Applications, Univ. of New South Wales, Sydney.
Nordin, H. (2003). “Fiber reinforced polymers in civil engineering—Flexural strengthening of concrete structures with prestressed near surface mounted CFRP rods.” MS thesis, Luleå Univ. of Technology, Luleå, Sweden.
Nordin, H., Carolin, A., and Täljsten, B. (2001). “Concrete beams strengthened with prestressed near surface mounted reinforcement (NSMR).” Proc., Int. Conf. on FRP Composites in Civil Engineering, J. G. Teng, ed., Hong Kong Polytechnic Univ., Hong Kong, 1067–1075.
Quantrill, R. J., and Hollaway, L. C. (1998). “The flexural rehabilitation of reinforced concrete beams by the use of prestressed advanced composite plates.” Compos. Sci. Technol., 58(8), 1259–1275.
Täljsten, B. (1994). “Plate bonding, strengthening of existing concrete structures with epoxy bonded plates of steel or fiber reinforced plastics.” PhD thesis, Luleå Univ. of Technology, Luleå, Sweden.
Täljsten, B. (1996). “Strengthening of concrete prisms using the plate-bonding technique.” Int. J. Fract., 82, 253–266.
Täljsten, B. (1997). “Strengthening of beams by plate bonding.” J. Mater. Civ. Eng., 9(4), 206–212.
Täljsten, B. (1998). “Förstärkning av betongkonstruktioner med stålplåt och avancerade kompositmaterial utsatta för vridning.” Forskningsrapport, Luleå Tekniska Universitet, Luleå, Sweden (in Swedish).
Täljsten, B. (2000). “Förstärkning av befintliga betongkonstruktioner med kolfiberväv eller kolfiberlaminat, Dimensionering, material och utförande.” Teknisk Rapport, Luleå Tekniska Universitet, Luleå, Sweden (in Swedish).
Täljsten, B. (2003a). “Strengthening concrete beams for shear with CFRP sheets.” Constr. Build. Mater., 17, 15–26.
Täljsten, B. (2003b). “Strengthening of existing concrete structures with externally bonded fibre reinforced polymers—Design and execution.” Technical Rep., Luleå Univ. of Technology, Luleå, Sweden.
Täljsten, B., and Carolin, A. (1999). “Strengthening of a concrete railway bridge in Luleå with carbon fibre reinforced polymers—CFRP: Load bearing capacity before and after strengthening.” Technical Rep. 1999:18, Luleå Univ. of Technology, Luleå, Sweden.
Täljsten, B., and Carolin, A. (2001). “CFRP strengthening, concrete beams strengthened with near surface mounted CFRP laminates.” Proc., FRPRC-5, Cambridge Univ., Cambridge, U.K. 107–116.
Täljsten, B., Carolin, A., and Nordin, H. (2003). “Concrete structures strengthened with near surface mounted reinforcement.” Adv. Struct. Eng., 6(3), 201–213.
Täljsten, B., and Elfgren, L. (2000). “Strengthening concrete beams for shear using CFRP materials: Evaluation of different application methods.” Composites, Part B, 31(2), 87–96.
Triantafillou, T. C., and Deskovic, N. (1991). “Innovative prestressing with FRP sheets: Mechanics of short-term behavior.” J. Eng. Mech., 117(7), 1652–1672.
Triantafillou, T. C., Deskovic, N., and Deuring, M. (1992). “Strengthening of concrete structures with prestressed fiber reinforced plastic sheet.” ACI Struct. J., 89(3), 235–244.
Wight, G., and Erki, M. A. (2001a). “CFRP strengthening of severely damaged reinforced concrete slabs.” Proc., Conf. on Concrete Under Severe Conditions—Environment and Loading, N. Banthia, K. Sakai,and O. E. Gjörv, eds., Univ. of British Columbia, Vancouver, Canada, 2191–2198.
Wight, G., and Erki, M. A. (2001b). “Prestressed CFRP for strengthening concrete slabs in fatigue.” Proc., Int. Conf. on FRP Composites in Civil Engineering, J. G. Teng, ed., Hong Kong Polytechnic Univ., Hong Kong.
Wight, R. G., Green, M. F., and Erki, M. A. (1995). “Post-strengthening concrete beams with prestressed FRP sheets.” Proc., Non-Metallic (FRP) Reinforcement for Concrete Structures, E&FN Spon, London.
Wight, R. G., Green, M. F., and Erki, M. A. (2001). “Prestressed FRP sheets for poststrengthening reinforced concrete beams.” J. Compos. Constr., 5(4), 214–220.
Information & Authors
Information
Published In
Journal of Composites for Construction
Volume 10 • Issue 1 • February 2006
Pages: 60 - 68
Copyright
© 2006 ASCE.
History
Received: Jul 19, 2004
Accepted: Oct 29, 2004
Published online: Feb 1, 2006
Published in print: Feb 2006
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.