Tests on reinforced concrete beams strengthened in shear using near surface mounted CFRP and steel bars

Abstract This paper presents the experimental results obtained from testing four large scale reinforced concrete T-beams strengthened in shear using near surface mounted (NSM) carbon fiber reinforced polymer (CFRP) bars and conventional steel reinforcing bars. The experimental program studied the effects of the orientation of the NSM bars, their type and their anchorage into the flange concrete. The tests showed that the NSM bars were engaged in the resistance as soon as they were crossed by a crack. The strengthening increased the shear capacity by 37%–92%, reduced the width of the diagonal cracks and allowed the beams to develop significant flexural ductility. The results also showed that orienting the NSM bars at 45° and extending their anchorage into the flange concrete improved the efficiency of strengthening. The CFRP strengthened test regions achieved 7%–10% larger shear capacity than the steel strengthened test regions, and their behavior was relatively similar.

[1]  Laura De Lorenzis,et al.  Behavior and capacity of RC beams strengthened in shear with NSM FRP reinforcement , 2009 .

[2]  Laura De Lorenzis,et al.  Modeling of debonding failure for RC beams strengthened in shear with NSM FRP reinforcement , 2009 .

[3]  Khaldoun N. Rahal,et al.  Minimum Transverse Reinforcement in 65 Mpa Concrete Beams , 2004 .

[4]  Giorgio Monti,et al.  Three dimensional mechanical model for simulating the NSM FRP strips shear strength contribution to RC beams , 2009 .

[5]  Daniel A. Kuchma,et al.  How Safe Are Our Large, Lightly Reinforced Concrete Beams, Slabs, and Footings? , 1999 .

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

[7]  Young Soo Yoon,et al.  Minimum Shear Reinforcement in Normal, Medium,and High-Strength Concrete Beams , 1996 .

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

[9]  J. Barros,et al.  Near surface mounted CFRP laminates for shear strengthening of concrete beams , 2006 .

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

[11]  C. Deniaud,et al.  Shear Behavior of Reinforced Concrete T-Beams with Externally Bonded Fiber-Reinforced Polymer Sheets , 2001 .

[12]  L. Lorenzis,et al.  Near-surface mounted FRP reinforcement: An emerging technique for strengthening structures , 2007 .

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

[14]  M. Badoux,et al.  Shear strength of URM walls retrofitted using FRP , 2006 .