An experimental and numerical study of the effect of thickness and length of CFRP on performance of repaired reinforced concrete beams

Abstract Experimental and numerical analyses are performed to predict the loading carrying capacity of reinforced concrete beams strengthened with carbon fibre reinforced plastics (CFRP) composites. The effect of CFRP thickness and length on the failure load and ductility is studied and curves of initial cracking load, ultimate load, stiffness, ductility and fibre stresses are presented. The results of tests and simulations show a good agreement and indicate that, in contrast with a control beam, initial cracking loads of strengthened beams increase slightly, whilst stiffness and ductility increase more and the ultimate loads increase considerably. Stresses in the carbon fibre decrease with the increase of fibre sheet thickness. Cracking patterns of strengthened beams are improved. Crack propagation varies with the change of fibre length and results in the variation of failure mode of beams. Variation of the length of CFRP sheet is the main reason of variation of the stress of interface. Therefore, debonding failure, unless adequately considered in the design process, may significantly decrease the effectiveness of the strengthening.

[1]  O. Büyüköztürk,et al.  Progress on understanding debonding problems in reinforced concrete and steel members strengthened using FRP composites , 2004 .

[2]  C. Leung.  Delamination Failure in Concrete Beams Retrofitted with a Bonded Plate , 2001 .

[3]  Yeoshua Frostig,et al.  Experiments and analytical comparison of RC beams strengthened with CFRP composites , 2003 .

[4]  Y. Frostig,et al.  Nonlinear High-Order Analysis of Cracked RC Beams Strengthened with FRP Strips , 2001 .

[5]  Deric J. Oehlers,et al.  Premature Failure of Externally Plated Reinforced Concrete Beams , 1990 .

[6]  Scott T Smith,et al.  Interfacial stresses in reinforced concrete beams bonded with a soffit plate: a finite element study , 2002 .

[7]  Lucie Vandewalle,et al.  Improved model for plate-end shear of CFRP strengthened RC beams , 2001 .

[8]  Peter Fajfar,et al.  Nonlinear seismic analysis and design of reinforced concrete buildings , 1992 .

[9]  M. Savoia,et al.  Non-linear model for R/C tensile members strengthened by FRP-plates , 2003 .

[10]  J.-L. Granju.  DEBONDING OF THIN CEMENT-BASED OVERLAYS , 2001 .

[11]  Scott T. Smith,et al.  Interfacial stresses in plated beams , 2001 .

[12]  T. Triantafillou.  Shear Strengthening of Reinforced Concrete Beams Using Epoxy-Bonded FRP Composites , 1998 .

[13]  Wai-Fah Chen,et al.  Constitutive equations for engineering materials , 1994 .

[14]  Wendel Michael Sebastian,et al.  SIGNIFICANCE OF MIDSPAN DEBONDING FAILURE IN FRP-PLATED CONCRETE BEAMS , 2001 .

[15]  Kin-tak Lau,et al.  Mechanical performance of composite-strengthened concrete structures , 2001 .

[16]  A. Ghobarah,et al.  Seismic rehabilitation of beam–column joint using GFRP sheets , 2002 .

[17]  K. Maekawa,et al.  Nonlinear mechanics of reinforced concrete , 2003 .