Shear Strengthening of RC T-Beams Using Mechanically Anchored Unbonded Dry Carbon Fiber Sheets
Publication: Journal of Performance of Constructed Facilities
Volume 24, Issue 1
Abstract
This research studies the feasibility and effectiveness of a new method of strengthening existing RC T-beams in shear by using mechanically anchored unbonded dry carbon fiber (CF) sheets. This method eliminates the debonding of epoxy-bonded carbon-fiber-reinforced polymer (CFRP) sheets and utilizes the full capacity of dry CF sheets. In this method, dry CF sheets are wrapped around and bonded to two steel rods. Then the rods are anchored to the corners of the web-flange intersection of the T-beam with mechanical bolts. This makes a U-shaped dry CF jacket around the web which increases the shear strength of the T-beam using the privilege of higher tensile strength and modulus of elasticity of dry CF compared to composite CFRP. A total of three RC T-beams with shear span-to-depth ratio of 2.0 were tested under increasing monotonic load till failure. The pilot tests were done as a proof-of-concept of the effectiveness of the proposed method in increasing the shear capacity of the RC T-beams. The first T-beam, which was tested as the control beam, failed in shear. The second beam was strengthened by using a U-shaped CFRP sheet that was externally bonded to the web of the beam in the shear zones. The third beam was strengthened by using anchored U-shaped dry CF sheet. The test results showed that the beam strengthened by the new mechanically anchored dry CF had about 48% increase in shear capacity as compared to the control beam and 16% increase in shear capacity as compared to the beam strengthened by CFRP epoxy-bonding method.
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Acknowledgments
The financial support of the Natural Sciences and Engineering Research Council of Canada (NSERC) through an operating grant is gratefully acknowledged.UNSPECIFIED
References
Adhikary, B. B., and Mutsuyoshi, H. (2004). “Behavior of concrete beams strengthened in shear with carbon-fiber sheets.” J. Compos. Constr., 8(3), 258–264.
Al-Sulaimani, G. J., Istem, A., Basunbul, A. S., Baluch, M. H., and Ghaleb, B. N. (1994). “Shear repair for reinforced concrete by fiberglass plate bonding.” ACI Struct. J., 91(3), 458–464.
American Association of State Highway Officials (AASHO). (1965). Standard specifications for highway bridges, 9th Ed., American Association of State Highway Officials, Washington, D.C.
American Concrete Institute (ACI). (1968). “Manual of concrete practice: Part 2.” Committee 318-1R-68, Detroit.
American Concrete Institute (ACI). (2008). “ACI 440.2R-08: Guide for design and construction of externally bonded FRP systems for strengthening concrete structures.” ACI Committee 440, Detroit.
Bousselham, A., and Chaallal, O. (2004). “Shear strengthening reinforced concrete beams with fiber-reinforced polymer: Assessment of influencing parameters and required research.” ACI Struct. J., 101(2), 219–227.
Canadian Standards Association (CSA). (2004). “Design of concrete structures.” CSA A23.3-04, Rexdale, Ont.
Canadian Standards Association (CSA). (2006). “Canadian highway bridge design code.” CSA S6-06, Rexdale, Ont.
Cao, S. Y., and Teng, J. G. (2005). “Debonding in RC beams shear strengthened with complete FRP wraps.” J. Compos. Constr., 9(5), 417–428.
Chajes, M. J., Januszka, T. F., Mertz, D. R., Thomson, T. A., and Finch, W. W. (1995). “Shear strength of RC beams using external applied composite fabrics.” ACI Struct. J., 92(3), 295–303.
Deniaud, C., and Cheng, J. J. R. (2003). “Reinforced concrete T-beams, strengthened in shear with fiber-reinforced polymer sheets.” J. Compos. Constr., 7(4), 302–310.
Fédération Internationale du Béton (fib). (2001). “Design and use of externally bonded FRP reinforcement (FRP EBR) for reinforced concrete structures.” fib Task Group 9.3 Technical Rep.
Fyfe Company LLC. (2007). Tyfo® SCH-11UP composite using Tyfo® S epoxy user’s guide, ⟨http://www.fyfeco.com⟩ (Feb. 22, 2007).
Higgins, C., Potisuk, T., Robelo, M. J., Farrow, W. C., McAuliffe, T. K., and Nicholas, B. S. (2007). “Tests of RC deck girders with 1950s vintage details.” J. Bridge Eng., 12(5), 621–631.
Hilti Corporation. (2007). HSL heavy duty sleeve anchor, ⟨http://www.ca.hilti.com⟩ (Sept. 7, 2007).
Hoult, N. A., and Lees, J. M. (2009). “Modelling of an unbonded CFRP strap shear retrofitting system for RC beams.” J. Compos. Constr., 13(4), 292–301.
Khalifa, A., Alkhrdaji, T., Nanni, A., and Lansburg, S. (1999). “Anchorage of surface mounted FRP reinforcement.” Concr. Int.: Des. Constr., 21(10), 49–54.
Khalifa, A., and Nanni, A. (2000). “Improving shear capacity of existing RC T-section beams using CFRP composites.” Cem. Concr. Compos., 22(3), 165–174.
Lees, J. M., Winistörfer, A. U., and Meier, U. (2002). “External prestressed carbon fiber-reinforced polymer straps for shear enhancement of concrete.” J. Compos. Constr., 6(4), 249–256.
Triantafillou, T. C. (1998). “Shear strengthening of reinforced concrete beams using epoxy-bonded FRP composites.” ACI Struct. J., 95(2), 107–115.
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© 2010 ASCE.
History
Received: Oct 27, 2008
Accepted: Jun 9, 2009
Published online: Jun 25, 2009
Published in print: Feb 2010
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