Title: Flexural strengthening of reinforced concrete beams using prestressed, near-surface-mounted CFRP bars
Date: Fall, 2011
Volume: 56
Issue: 4
Page number: 134-151
Author(s): Raafat El-Hacha, Mohamed Gaafar
https://doi.org/10.15554/pcij.09012011.134.151
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Abstract
Near-surface-mounted (NSM) fiber-reinforced polymer (FRP) is an efficient system for strengthening reinforced concrete beams. The FRP is embedded in grooves in the concrete cover on the tension side of the member. When the FRP is not prestressed, the system can support additional loads applied to the structure but is unable to carry the dead load. Previous researchers showed that premature failure may occur in beams strengthened with nonprestressed NSM FRP, leading to failure in beams without reaching the full designed capacity. This paper reports the findings of an experimental investigation into the effectiveness of using prestressed NSM carbon FRP (CFRP) bars to strengthen reinforced concrete beams. The effect of varying the prestressing levels in the CFRP bars on the behavior of the beams was examined. Five large-scale reinforced concrete beams were tested: one control, one strengthened with nonprestressed NSM CFRP bars, and three strengthened with NSM CFRP bars prestressed to 20%, 40%, and 60% of the ultimate strength of the CFRP. The flexural behavior of the prestressed concrete beams is compared with the nonprestressed beam and the control. Test results showed that all prestressed concrete beams failed due to rupture of the CFRP bars without any premature or debonding failure. Prestressing the embedded NSM CFRP reinforcement enhanced the overall performance of the beams by increasing the loads at cracking, yielding, and ultimate. Due to the prestressing effect, the deflections in the strengthened beams corresponding to the cracking, yielding, and ultimate loads of the unstrengthened beam are less than the deflections at the same loads of the unstrengthened beam as well as at those of the strengthened beam with nonprestressed CFRP reinforcement.
References
1. El-Hacha, R., and S. H. Rizkalla. 2004. Near Surface Mounted FRP Reinforcements for Flexural Strengthening of Concrete Structures. ACI Structural Journal, V. 101, No. 5 (September–October): pp. 717–726.
2. Castro, E. K., G. S. Melo, and Y. Nagato. 2007. Flexural Strengthening of RC “T” Beams with Near Surface Mounted (NSM) FRP Reinforcement. In Proceedings of the 8th International Symposium on Fiber Reinforced Polymer Reinforcement for Reinforced Concrete Structures (FRPRCS-8), July 16–18, 2007. Patras, Greece: University of Patras. CD-ROM.
3. Choi, H. T., J. S. West, and K. A. Soudki. 2007. An Experimental Study on the Flexural Response of Partially Bonded FRP Strengthened Concrete Beams. In Proceedings of the 8th International Symposium on Fiber Reinforced Polymer Reinforcement for Reinforced Concrete Structures (FRPRCS-8), July 16–18, 2007. Patras, Greece: University of Patras. CD-ROM.
4. Derias, M., R. El-Hacha, and S. Rizkalla. 2008. Durability of Various NSM FRP Strengthening Systems for RC Flexural Members. In Proceedings of the 5th International Conference on Advanced Composite Materials in Bridges and Structures (ACMBS-V), September 22–24, 2008. Montréal, Québec, Canada: Canadian Society for Civil Engineering. CD-ROM.
5. El-Hacha, R., S. H. Rizkalla, and R. Kotynia. 2005. Modeling of Reinforced Concrete Flexural Members Strengthened with Near-Surface Mounted FRP Reinforcement. In Proceedings of the 7th International Symposium on Fiber-Reinforced Polymer Reinforcement for Concrete Structures (FRPRCS-7), Special Publications SP-230, November 6–9, 2005, pp. 1681–1700. Farmington Hills, MI: American Concrete Institute. CD-ROM.
6. Filho, J. N. S., G. S. S. Melo, R. El-Hacha, S. Rizkalla, and R. Carneiro. 2005. Finite Element Modeling (FEM) of RC Beams Strengthened in Flexure with FRP. In Proceedings of the 47th International Concrete Brazilian Congress (IBRACON), September 2–7, 2005. San Paulo, Brazil: Brazilian Concrete Institute. CD-ROM.
7. El-Hacha, R., J. N. S. Filho, S. H. Rizkalla, and G. S. Melo. 2004. Effectiveness of Near Surface Mounted FRP Reinforcements for Flexural Strengthening of RC Concrete Beams. In Proceedings of the 4th International Conference on Advanced Composite Materials in Bridges and Structures (ACMBS-IV), July 20–23,2004. Montréal, Québec, Canada: Canadian Society for Civil Engineering. CD-ROM.
8. Filho, J. N. S., G. S. S. Melo, R. El-Hacha, and S. Rizkalla. 2005. Fatigue Behaviour of RC Beams Strengthened in Flexure with Externally Bonded and Near Surface Mounted FRP Reinforcements. In roceedings of the 47th International Concrete Brazilian Congress (IBRACON), September 2–5, 2005. São Paulo, Brazil: Brazilian Concrete Institute. CD-ROM.
9. Kishi, N., H. Mikami, Y. Kurihashi, nd S. Sawada. 2005. Flexural Behaviour of RC Beams Reinforced with NSM AFRP Rods. In Proceedings of the International Symposium on Bond Behaviour of FRP in structures (BBFS 2005), December 7–9, 2005, pp. 337–342. Hong Kong, China: International Institute for FRP in Construction.
10. Kotynia, R. 2007. Analysis of the Flexural Response of NSM FRP-Strengthened Concrete Beams. In Proceedings of the 8th International Symposium on Fiber Reinforced Polymer Reinforcement for Reinforced Concrete Structures (FRPRCS-8), July 16–18, 2007. Patras, Greece: University of Patras. CD-ROM.
11. Täljsten, B., and H. Nordin. 2006. Concrete Beams Strengthened with External Prestressing Using External Tendons and Near-Surface-Mounted Reinforcement (NSMR). In proceedings of Case Histories and Use of FRP for Prestressing Applications, Special Publications SP-245, November 8, 2006, pp. 143–164. Farmington Hills, MI: American Concrete Institute. CD-ROM.
12. Carolin, A., H. Nordin, and B. Täljsten. 2001. Concrete Beams Strengthened with Near Surface Mounted Reinforcement of CFRP. In Proceedings of the International Conference on FRP Composites in Civil Engineering, Hong Kong, China, December 12–15, V. 2, pp. 1059–1066. Oxford, UK: Elsevier Science.
13. Novidis, D. G., and S. J. Pantazopoulou. 2007. Beam Tests of NSM-FRP Laminates in Concrete. In Proceedings of the 8th International Symposium on Fiber Reinforced Polymer Reinforcement for Reinforced Concrete Structures (FRPRCS-8), July 16–18, 2007. Patras, Greece: University of Patras. CD-ROM.
14. Jung, W.-T., Y.-H. Park, J.-S. Park, J.-Y. Kang, and Y.- J. You. 2005. Experimental Investigation on Flexural Behavior of RC Beams Strengthened by NSM CFRP Reinforcements. In Proceedings of the 7th International Symposium on Fiber Reinforced Polymer Reinforcement for Reinforced Concrete Structures (FRPRCS-7), Special Publications SP-230, November 7–10, 2005, pp. 795–805, Kansas ity, MO. Farmington Hills, MI: American Concrete Institute. CD-ROM.
15. De Lorenzis, L., and A. Nanni. 2002. Bond Between Near-Surface Mounted FRP Rods and Concrete in Structural Strengthening. ACI Structural Journal, V. 99, No. 2 (March–April): pp. 123–132.
16. Hassan, T., and S. Rizkalla. 2003. Investigation of Bond in Concrete Structures Strengthened with Near Surface Mounted Carbon Fiber Reinforced Polymer Strips. Journal of Composites for Construction, V. 7, No. 3 (August): pp. 248–257.
17. Hassan, T., and S. Rizkalla. 2004. Bond Mechanism of NSM FRP Bars for Flexural Strengthening of Concrete Structures. ACI Structural Journal, V. 101, No. 6 (November–December): pp. 830–839.
18. Thorenfeldt, E. 2007. Bond Capacity of CFRP Strips Glued to Concrete in Sawn Slits. In Proceedings of the 8th International Symposium on Fiber Reinforced Polymer Reinforcement for Reinforced Concrete Structures(FRPRCS-8), July 16–18, 2007. Patras, Greece: University of Patras. CD-ROM.
19. Casadei, P., N. Galati, G. Boschetto, K. Y. Tan, A. Nanni, and G. Galecki. 2006. Strengthening of Impacted Prestressed Concrete Bridge I-Girder Using Prestressed Near Surface Mounted C-FRP Bar. Fédération Internationale du Béton (FIB), Proceedings of the 2nd International Congress, June 5–8, 2006, Naples, Italy, Session 10. Lausanne, Switzerland: FIB.
20. Jung, W., J. Park, and Y. Park. 2007. A Study on the Flexural Behavior of Reinforced Concrete Beams Strengthened with NSM Prestressed CFRP Reinforcement. In Proceedings of the 8th International Symposium on Fiber Reinforced Polymer Reinforcement for Reinforced Concrete Structures (FRPRCS-8), July 16–18, 2007. Patras, Greece: University of Patras. CD-ROM.
21. Nordin, H. 2003. Flexural Strengthening of Concrete Structures with Prestressed Near Surface Mounted CFRP Rods. PhD thesis, Department of Civil and Mining Engineering, Division of Structural Engineering, Luleå University of Technology, Sweden.
22. Nordin, H., and B. Täljsten. 2006. Concrete Beams Strengthened with Prestressed Near Surface Mounted CFRP. Journal of Composites for Construction, V. 10, No. 1 (January–February): pp. 60–68.
23. Wu, Z., K. Iwashita, and X. Sun. 2005. Structural Performance of RC Beams Strengthened with Prestressed Near-Surface-Mounted CFRP Tendons. In Proceedings of the 7th International Symposium on Fiber Reinforced Polymer Reinforcement for Reinforced Concrete Structures (FRPRCS-7), SP-230, Kansas City, Missouri, November 7–10, 2005, pp. 165–178. Farmington Hills, MI: American Concrete Institute. CD-ROM.
24. Gaafar, M. A., and R. El-Hacha. 2008. Innovative System to Strengthen Reinforced Concrete Beams with Prestressed FRP NSM Technique. In Proceedings of the 5th International Conference on Advanced Composite Materials in Bridges and Structures (ACMBS-V), Winnipeg, Manitoba, Canada, September 22–24, 2008. Montréal, Québec, Canada: Canadian Society for Civil Engineering. CD-ROM.
25. ASTM Subcommittee A01.13. 2002. Standard Test Methods and Definitions for Mechanical Testing of Steel Products. ASTM A370-02. West Conshohocken, PA: ASTM International.
26. ASTM Subcommittee C09.61. 2000. Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory. ASTM C192/C192M-00. West Conshohocken, PA: ASTM International.
27. Canadian Standards Association (CSA). 2004. Design of Concrete Structures. CSA A23.3-04. Mississauga, Ontario, Canada: CSA.
28. The Canadian Networks of Centers of Excellence on Intelligent Sensing for Innovative Structures, (ISIS Canada). 2001. Strengthening Concrete Structures with Externally-Bonded Fiber Reinforced Polymers (FRPs). ISIS M04-01, Design Manual No. 4. Winnipeg, Manitoba, Canada: University of Manitoba.
29. Hughes Brothers Inc. 1999. Hughes Brothers Reinforcements. Product Guide Specification. Seward, NE: Hughes Brothers Inc.
30. ACI Committee 440. 2004. Guide Test Methods for Fiber-Reinforced Polymers (FRPs) for Reinforcing or Strengthening Concrete Structures. ACI 440.3R-04. Farmington Hills MI: American Concrete Institute.
31. Gaafar, M. 2007. Strengthening Reinforced Concrete Beams with Prestressed Near Surface Mounted Fibre Reinforced Polymers. MSc thesis, University of Calgary, Canada.