Contribution of Externally Bonded FRP to Shear Capacity of RC Flexural Members

Abstract

Fiber reinforced polymer (FRP) materials are continuing to show great promise for use in strengthening reinforced concrete (RC) structures. These materials are an excellent option for use as external reinforcing because of their light weight, resistance to corrosion, and high strength. Externally bonded FRP sheets have been used to increase moment capacity of flexural members and to improve confinement in compression members.Investigations into the use of externally bonded FRP sheets for use in shear strengthening have also been conducted and have shown this to be a viable strengthening method. The objective of this study is to review the current research on shear strengthening with FRP and propose design algorithms to compute the contribution of FRP to the shear capacity of RC flexural members. Methods for computing the shear capacity based on the stress level to cause tensile fracture of the FRP sheet (which may be less than ultimate due to stress concentrations) and based on delamination of the sheet from the concrete surface are presented. Areas which have the potential for further development are also discussed.

Shear strengthening of reinforced concrete beams with CFRP

“…Current American Concrete Institute (ACI 2002 andInternational Federation for Concrete 2001) design guidelines for strengthening RC beams in shear with CFRP are based on empirical design equations derived by Khalifa et al (1998) and Triantafillou and Antonopoulos (2000) respectively. The nominal shear strength 'V n ' is calculated by adding individual contributions calculated for the concrete 'V c ', internal steel stirrups 'V s ', and external FRP composites 'V f ' resulting in the general equation…”

“…He went on to derive an empirical relationship between strain and axial rigidity with data from 40 beams tested by various researchers. Khalifa et al (1998) modified Triantafillou's (1998) method for calculating å fe on the basis of a slightly enlarged data base of 48 beams. The experimental data used by Khalifa et al (1998) included two types of FRP materials (carbon and aramid) and three different wrapping configurations (sides only, U-shaped wrapping and complete wrapping), with both continuous sheets and strips of FRP.…”

Structural Behavior of Strengthened RC Beams in Shear using CFRP Strips

“…Results show that the CFRP sheets can provide increase in strength and stuffiness to existing concrete beams when bonded to the web and tension face. Khalif et al (1998) [13], used a slight modification (Triantafillou's equation 1998) to define shear failure combined with FRP rupture. Meanwhile, the bond model of Maeda et al 1997 [14], was used to describe shear failure combined with CFRP debonding.…”

Full-range FRP failure behaviour in RC beams shear-strengthened with FRP wraps

“…Extensive studies carried out over the past two decades on RC beams ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T shear-strengthened with EB FRP (Bousselham and Chaallal, 2004, 2006a, b, 2008Carolin and Taljsten, 2005a;Islam et al, 2005;Khalifa et al, 1998;Nanni, 2000, 2002;Leung et al, 2007;Matthys, 2000;Monti and Liotta, 2007;Pellegrino and Modena, 2002Taljsten, 2003;Triantafillou, 1998) have led to many design models (Carolin and Taljsten, 2005b;Chaallal et al, 1998;Chajes et al, 1995;Chen and Teng, 2003a, b;Khalifa et al, 1998;Mofidi and Chaallal, 2011;Monti and Liotta, 2007;Pellegrino and Modena, 2002Taljsten, 2003;Triantafillou, 1998;Triantafillou and Antonopoulos, 2000;Ye et al, 2005), some of which have been adopted in design guidelines (ACI-440.2R, 2008;CNR-DT-200R1, 2013;Concrete-Society, 2012;fib, 2001;GB50608-2010GB50608- , 2010HB305, 2008;JSCE, 2001). The majority of these existing design models have assumed that the shear capacity of the EB FRP shear-strengthened beam (V u ) is a sum of the shear contributions of concrete (V c ), steel shear reinforcements (V s ) and shear strengthening FRP (V f ) based on simple superposition (i.e.…”

“…Based on the limited test results of small specimens (Khalifa et al, 1998;Priestley and Seible, 1995), existing guidelines normally recommend a strain limit in the range of 0.004  0.006 (e.g. 0.004 in ACI 440-2R (2008) and 0.006 in fib (2001)), to avoid a significant degradation of the concrete shear resistance.…”