The effects of NSM CFRP reinforcements for improving the shear capacity of RC beams

Abstract One of the most efficient technique for improving the shear strength of deteriorated RC members is bonding external carbon fiber-reinforced polymer (CFRP) composites. However, delimitation and debonding of the strengthening material frustrates to achieve the expected requirements. Near surface mounting (NSM) is a recent strengthening technique that was developed with the anticipation of obstructing the drawbacks of external CFRP usage. To demonstrate the efficiency, an experimental program was conducted to validate the effect of CFRP reinforcements on behavior and ultimate strength of shear deficient (without stirrups) reinforced concrete (RC) beams under cyclic loading. Accordingly seven of eight beams except the flexural reference were fabricated and strengthened with CFRP reinforcements with distinct CFRP reinforcement arrangements. Spacing of CFRP reinforcements, variation of CFRP reinforcement diameter and application of CFRP reinforcements were the selected variables of the experimental program. Tests results confirmed that all in all an increase in strength was seen in every specimen to which CFRP reinforcements applied with no occurrence of delamination, debonding or fracture of CFRP reinforcements. To verify the reliability, experimental results were compared with ACI-440 guideline and the proposals of De Lorenzis and Nanni.

[1]  Hiroshi Mutsuyoshi,et al.  Shear strengthening of reinforced concrete beams using steel plates bonded on beam web: experiments and analysis , 2000 .

[2]  A. K. M. Anwarul Islam,et al.  Effective methods of using CFRP bars in shear strengthening of concrete girders , 2009 .

[3]  Arnaud Castel,et al.  Strengthening of RC members with near-surface mounted CFRP rods , 2009 .

[4]  Antonio Nanni,et al.  Characterization of FRP Rods as Near-Surface Mounted Reinforcement , 2001 .

[5]  Luciano Ombres,et al.  Prediction of intermediate crack debonding failure in FRP-strengthened reinforced concrete beams , 2010 .

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

[7]  Antonio Nanni,et al.  Shear Strengthening of Reinforced Concrete Beams with Near-Surface Mounted Fiber-Reinforced Polymer Rods , 2001 .

[8]  Ayaho Miyamoto,et al.  Behavior of Prestressed Beam Strengthened with External Tendons , 2000 .

[9]  A. Nanni,et al.  Contribution of Externally Bonded FRP to Shear Capacity of RC Flexural Members , 1998 .

[10]  R. Capozucca,et al.  Static and dynamic response of damaged RC beams strengthened with NSM CFRP rods , 2009 .

[11]  Gaetano Manfredi,et al.  Behavior and Modeling of Bond of FRP Rebars to Concrete , 1997 .

[12]  J. Barros,et al.  Near surface mounted CFRP-based technique for the strengthening of concrete structures , 2004 .

[13]  Stephanie L. Walkup,et al.  Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures (ACI 440.2R-02) , 2005 .

[14]  Zhishen Wu,et al.  PREDICTION OF CRACK-INDUCED DEBONDING FAILURE IN R/C STRUCTURES FLEXURALLY STRENGTHENED WITH EXTERNALLY BONDED FRP COMPOSITES , 2007 .

[15]  R. Narayan Swamy,et al.  Contribution of Externally Bonded Steel Plate Reinforcement to the Shear Resistance of Reinforced Concrete Beams , 1996 .

[16]  J. Barros,et al.  Efficacy of CFRP-based techniques for the flexural and shear strengthening of concrete beams , 2007 .

[17]  Alex Li,et al.  Shear strengthening effectiveness with CFF strips , 2003 .

[18]  Costas P. Antonopoulos,et al.  Design of Concrete Flexural Members Strengthened in Shear with FRP , 2000 .

[19]  Antonio Nanni,et al.  Bond between Near-Surface Mounted Fiber-Reinforced Polymer Rods and Concrete in Structural Strengthening , 2002 .

[20]  Issam E. Harik,et al.  SHEAR STRENGTH OF R/C BEAMS WRAPPED WITH CFRP FABRIC , 2002 .

[21]  S. Rizkalla,et al.  Near-Surface-Mounted Fiber-Reinforced Polymer Reinforcements for Flexural Strengthening of Concrete Structures , 2004 .

[22]  Deric J. Oehlers,et al.  Study of Intermediate Crack Debonding in Adhesively Plated Beams , 2007 .