Rectangular Reinforced Concrete Beams Strengthened with CFRP Straps
Publication: Journal of Composites for Construction
Volume 18, Issue 1
Abstract
Shear-deficient reinforced concrete (RC) structures can be effectively strengthened using external prestressed carbon fiber–reinforced polymer (CFRP) straps. Due to the presence of the external elastic straps, a strengthened beam can continue to carry significant load beyond the stages of crack plane slipping and internal-shear stirrup yielding, and the concrete is subjected to high tensile strain levels. As a consequence, the concrete material models play a significant role in the context of modeling such behavior. The modified compression field theory (MCFT), which is a widely accepted shear theory for unstrengthened RC structures, incorporates the details of the stress-strain behavior of concrete. The MCFT also considers compatibility as a governing factor, which facilitates the inclusion of the strap system into the MCFT formulation. In the current study, modifications were investigated to model CFRP strap retrofitted RC beams associated with either uniform or nonuniform strap spacings. An experimental investigation on strengthened and unstrengthened rectangular RC beams was carried out to validate the MCFT predictions for various strap layouts. The validation process revealed that, in general, the MCFT was able to model the shear response of the retrofitted RC beams, but the representation of the softening of the concrete compressive strain, and stress, was found to be influential in the determination of the ultimate load capacity.
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Acknowledgments
The first author is grateful for the financial support provided by the Cambridge Commonwealth Trust, the Overseas Research Studentship, and the Churchill College. The authors are also appreciative of the technical support and assistance provided by EMPA, Dr. N. A. Hoult, Dr. C. T. Morley, Mr. M. R. Touhey, and Mr. S. J. Holder.
References
Acevedo, A. B., Bentz, E. C., and Collins, M. P. (2009). “Influence of clamping stresses in the shear strength of concrete slabs under uniform loads.” J. Earthquake Eng., 13(S1), 1–17.
Bentz, E. C. (2000). “Sectional analysis of reinforced concrete.” Ph.D. thesis, Dept. of Civil Engineering, Univ. of Toronto, Toronto, ON, Canada.
Collins, M. P., and Mitchell, D. (1987). Prestressed concrete basics, Canadian Prestressed Concrete Institute, Ottawa, ON, Canada.
Dirar, S., Lees, J. M., and Morley, C. (2013). “Precracked reinforced concrete T-beams repaired in shear with carbon fiber-reinforced polymer straps.” ACI Struct. J., 110(5), 855–865.
Duthinh, D. (1999). “Sensitivity of shear strength of reinforced concrete and prestressed concrete beams to shear friction and concrete softening according to modified compression field theory.” ACI Struct. J., 96(4), 495–508.
Hoult, N. A., and Lees, J. M. (2009). “Efficient CFRP strap configurations for the shear strengthening of reinforced concrete T-beams.” J. Compos. Constr., 45–52.
Hoult, N. A., and Lees, J. M. (2011). “Time-dependent behavior of RC beams retrofitted with CFRP straps.” J. Compos. Constr., 75–84.
Kesse, G., and Lees, J. M. (2007). “Experimental behaviour of reinforced concrete beams strengthened with prestressed CFRP shear straps.” J. Compos. Constr., 375–383.
Lees, J. M., and Winistörfer, A. U. (2011). “Non-laminated FRP strap elements for reinforced concrete, timber and masonry applications.” J. Compos. Constr., 146–155.
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., 249–256.
Teng, J. G., Chen, J. F., Smith, S. T., and Lam, L. (2003). “Behaviour and strength of FRP-strengthened RC structures: A state-of-the-art review.” Proc. Inst. Civ. Eng. Struct. Build., 156(1), 51–62.
Vecchio, F. J., and Collins, M. P. (1986). “The modified compression field theory for reinforced concrete elements subjected to shear.” ACI Struct. J., 83(2), 219–231.
Vecchio, F. J., and Collins, M. P. (1993). “Compression response of cracked reinforced concrete.” J. Struct. Eng., 3590–3610.
Winistörfer, A. U. (1999). “Development of non-laminated advanced composite straps for civil engineering applications.” Ph.D. thesis, Dept. of Engineering, Univ. of Warwick, Coventry, U.K.
Yapa, H. D. (2011). “Optimum shear strengthening of reinforced concrete beams.” Ph.D. thesis, Dept. of Engineering, Univ. of Cambridge, Cambridge, U.K.
Yapa, H. D., and Lees, J. M. (2011). “Analysis of CFRP strap-strengthened reinforced concrete beams using the modified compression field theory (MCFT).” Fiber-reinforced polymer (FRP) reinforcement for concrete structures, American Concrete Institute, Farmington Hills, MI, SP 275, 1–20.
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Published In
Journal of Composites for Construction
Volume 18 • Issue 1 • February 2014
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Feb 27, 2013
Accepted: Jul 11, 2013
Published online: Jul 13, 2013
Published in print: Feb 1, 2014
Discussion open until: Mar 21, 2014
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