Near surface mounted (NSM) technique has proved to be a very effective technique for the flexural strengthening of RC beams. Due to the relatively small thickness of the concrete cover that several beams present, cutting the bottom arm of steel stirrups for the installation of NSM laminates might be a possible strategy, whose implications on the beam's load carrying capacity need to be assessed. When steel stirrups are cut, however, the shear resistance can be a concern. This also happens when a strengthening intervention is carried out to increase the flexural resistance of a beam, since in certain cases it is also necessary to increase the shear resistance in order to avoid the occurrence of brittle shear failure. The present work assesses the effectiveness of a technique that aims to increase both the flexural and shear resistance of RC beams that have the bottom arm of the steel stirrups cut for the application of NSM laminates. This assessment is performed by experimental and numerical research. The main results of the experimental program are presented and analyzed, and the innovative aspects of a constitutive model implemented in a computer program are described, being their virtues and deficiencies discussed.
ACI Committee 440 (2007). Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures, American Concrete Institute, Farmington Hills, MI, USA.
2.
BarrosJ.A.O.FortesA.S. (2005). “Flexural strengthening of concrete beams with CFRP laminates bonded into slits”, Journal Cement and Concrete Composites, Vol. 27, No. 4, pp. 471–480.
3.
BarrosJ.A.O.DiasS.J.E.LimaJ.L.T. (2007). “Efficacy of CFRP-based techniques for the flexural and shear strengthening of concrete beams”, Journal of Cement and Concrete Composites, Vol. 29, No. 3, pp. 203–217
4.
BarrosJ.A.O.DalfréG.M.DiasJ.P.S.E. (2008). “Numerical simulation of continuous RC slabs strengthened using NSM technique”, Proceedings of the 2nd International Conference on Concrete Repair, Rehabilitation and Retrofitting, ICCRRR-2008, Cape Town, South Africa, November.
5.
BarrosJ.A.O.DiasS.J.E.LimaJ.L.T. (2008). “Analytical and numerical analysis of the behaviour of RC beams flexural strengthened with CFRP”, Proceedings of the Fourth International Conference on FRP Composites in Civil Engineering, CICE-2008, Zurich, Switzerland, July.
6.
BiancoV. (2009). Shear Strengthening of RC Beams by Means of NSM CFRP Strips: Experimental Evidence and Analytical Modellin, PhD Thesis, Sapienza University of Rome, Italy.
7.
BonaldoE.BarrosJ.A.O.LourençoP.J.B. (2008). “Efficient strengthening technique to increase the flexural resistance of existing RC slabs”, Journal of Composites for Construction, ASCE, Vol. 12, No. 2, pp. 149–159.
8.
CEB-FIP (1993). CEB-FIP Model Code 1990: Design Code, Thomas Telford, Lausanne, Switzerland.
9.
El-HachaR.RizkallaS.H. (2004). “Near-surface-mounted fiber-reinforced polymer reinforcements for flexural strengthening of concrete structures”, ACI Structural Journal, Vol. 101, No. 5, pp. 717–726.
10.
fib Bulletin 14. (2001). Externally Bonded FRP Reinforcement for RC Structures, Technical report by Task Group 9.3, International Federation for Structural Concrete, Lausanne, Switzerland.
11.
HaskettM.H.OehlersD.J.WuC. (2007). “Improved IC debonding resistance of embedded NSM FRP plates”, Proceedings of Asia-Pacific Conference on FRP in Structures, APFIS-2007, Hong Kong, China, December.
12.
LiuI.S.T.OehlersD.J.SeracinoR. (2006). “Tests on the ductility of reinforced concrete beams retrofitted with FRP and steel near-surface mounted plates”, Journal of Composites for Construction, ASCE, Vol. 10, No. 2, pp. 106–114.
13.
KotyniaR. (2005). “Strain efficiency of near surface mounted CFRP-strengthened reinforced concrete beams”, Proceedings of International Conference on Challenges for Civil Construction, Lyon, France, July.
14.
KotyniaR. (2006). “Analysis of reinforced concrete beams strengthened with near surface mounted FRP reinforcement”, Archives of Civil Engineering, Vol. 52, No. 2, pp. 305–317.
15.
LimaJ.L.T.BarrosJ.A.O. (2007). “Design models for shear strengthening of reinforced concrete beams with externally bonded FRP composites: A statistical vs. reliability approach”, Proceedings of the 8th International Symposium on Fiber Reinforced Polymer Reinforcement for Concrete Structures, FRPRCS-8, University of Patras, Patras, Greece, July.
16.
RotsJ.G.de BorstR. (1987). “Analysis of mixed-mode fracture in concrete”, Journal of Engineering Mechanics, ASCE, Vol. 113, No. 11, pp. 1739–1758.
17.
RotsJ.G. (1988). Computational Modeling of Concrete Fracture, PhD Thesis, Delft University of Technology, The Netherlands.
18.
SantosP.F.S.BarrosJ.A.O.LourençoL.A.P. (2008). “Steel fibres for the shear resistance of high strength concrete beams”, Proceedings of the 7th RILEM International Symposium on Fibre Reinforced Concrete Design and Applications, BEFIB-2008, Chennai (Madras), India, September.
19.
SasG.TäljstenB.BarrosJ.A.O.LimaJ.L.T.CarolinA. (2009). “Are available models reliable for predicting the FRP contribution to the shear resistance of RC beams?”, Journal of Composites for Construction, ASCE, Vol. 13, No. 6, pp. 514–534.
20.
Sena-CruzJ.M.BarrosJ.A.O.AzevedoA.F.M.Ventura-GouveiaA. (2007). “Numerical simulation of the nonlinear behavior of RC beams strengthened with NSM CFRP strips”, Proceedings of CMNE/CILAMCE, FEUP, Porto, June.
21.
Sena-CruzJ.M. (2004). Strengthening of Concrete Structures with Near-Surface Mounted CFRP Laminate Strips, PhD Thesis, Department of Civil Engineering, University of Minho, Portugal.
22.
Sena-CruzJ.M.BarrosJ.A.O. (2004a). “Bond between near-surface mounted CFRP laminate strips and concrete in structural strengthening”, Journal of Composites for Construction, ASCE, Vol. 8, No. 6, pp. 519–527.
23.
Sena-CruzJ.M.BarrosJ.A.O. (2004b). “Modeling of bond between near-surface mounted CFRP laminate strips and concrete”, Computers and Structures, Vol. 82, No. 17–19, pp. 1513–1521.
24.
Sena-CruzJ.M.BarrosJ.A.O.AzevedoA.F.M.GettuR. (2006). “Bond behavior of near-surface mounted CFRP laminate strips under monotonic and cyclic loading”, Journal of Composites for Construction, ASCE, Vol. 10, No. 4, pp. 295–303.
25.
StevensN.J. (1987). Analytical Modelling of Reinforced Concrete Subjected to Monotonic and Reversed Loadings, Publication No. 87-1, Department of Civil Engineering, University of Toronto.
26.
TäljstenB.CarolinA.NordinH. (2003). “Concrete structures strengthened with near surface mounted reinforcement of CFRP”, Advances in Structural Engineering, Vol. 6, No. 3, pp. 201–213.
27.
Ventura-GouveiaA.BarrosJ.A.O.AzevedoA.F.M.Sena-CruzJ.M. (2008). “Multifixed smeared 3D crack model to simulate the behavior of fiber reinforced concrete structures”, Proceedings of the International Conference on Challenges for Civil Construction, CCC-2008, Porto, Portugal, April.
