Moment Capacity Charts for Strengthening of RC Beams With Near Surface Mounted FRP Reinforcement

Mohamad R. Abdulkadir and Avin H. Abdullah MSc

Departement of Civil Engineerng, Faculty of Engineering, University of Sulaimani,


Near surface- mounted fibre reinforced polymer is a new technique for strengthening
structural members beside externally applied fibre reinforced polymer (FRP) technology.
In NSM technique, the FRP material is applied to the tension region of the member inside
pre-prepared grooves. In externally applied FRP the debonding of the fibres is a major
issue thus, the full utilisation of FRP material can not be achieved, and the fibres are more
susceptible to environmental effects. With NSM FRP, these issues can be controlled more
effectively. ACI Committee 440 [1] has presented guidelines for design and construction
of externally FRP method for strengthening of concrete structures. Although many
experiments have been conducted on NSM FRP in flexure strengthening of RC beams,
no code is introduced yet. Theoretical studies to derive equations for calculating moment
capacity of strengthened beams have been introduced but mostly require several trial
procedures to reach the required effective strain for FRP. In this study, a moment
capacity chart is introduced based on several assumptions in the derivation of flexure
capacity equation. To avoid the brittle behaviour of FRP, it is suggested that the
utilization of FRP to be limited to 70% of its ultimate capacity for CFRP, and an
equivalent area of reinforcement is adopted for simplicity. Experimental results of other
researchers have been verified with the proposed charts, and a good comparison of results
have being achieved.

Key Words:
fibre reinforced
moment capacity


[1]  ACI440.IR-02 “Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures”, American concrete institute, Farmington Hills Michigan. (2002).

[2]  Fib TC. “Externally bonded FRP reinforcement for RC structures”, International Federation for structural concrete, Lausanne. (2001).

[3]  Delorenzis, L. and Nanni, A. “Bond between near-surface mounted fibre-reinforced polymer rods and concrete in structural strengthening”, ACI-Structural Journal, Vol. (99), No. S13, pp. 123-132. (2002).

[4]  Yost, J. R., Gross, S. P., Dinehart, D. W. and Mildenberg, J.J “Flexural behaviour of concrete beams strengthened with near-surface-mounted CFRP strips”. ACI-Structural Journal, Vol. (104), No. S41, pp. 430-437. (2007).

[5]  Delorenzis, L., Nanni, A. and Tegola, A. La “Strengthening of Reinforced structures with  near                      surface mounted FRP rods”, (2000). [online] available from <> [2 July 2013]

[6]   El-Hacha, R. and Rizkalla, S. H. “Near Surface Mounted Fibre Reinforced Polymer Reinforcements               for Flexural Strengthening of Concrete Structures”, ACI-Structural Journal, Vol. (101), No. S71, pp.            717-726. (2004).

[7]  Jung, W.,T., Park, Y.,H., Park, J., S., Kang, J., Y. and You, Y.,J. “Experimental investigation on flexural behaviour of RC beams strengthened by NSM CFRP reinforcements”, (2005). [online] available from <> [2 July 2013]

[8]  Badawi M, Soudki K. “Flexural strengthening of RC beams with prestressed NSM CFRP rods – experimental and analytical investigation”, Construction and building materials, Vol. (23)No. 10, pp. 292–300. (2009).

[9]  Delorenzis, L. “Strengthening of RC structures with near surface mounted FRP rods”, PhD  Thesis, Department of Innovation Engineering, Univerity of Lecce, Italy. (2002).  

[10] Sharaky, A., Torres, L., Beana, M. and Vilanova, I. “Effect of different material and construction          details on the bond behaviour of NSM FRP bars in concrete”, Construction and building materials, Vol.         (38), pp. 890-902. (2012) 

[11] Hassan, T. and Rizkalla, S. “Bond mechanism of near-surface-mounted fibre –reinforced polymer bars for flexural strengthening of concrete structures”, ACI-Structural Journal, Vol. (101), No. S82, pp. 830-839. (2004)

[12] Al-Mahmoud, F., Castel, A., Francois, R. and Tourneur, C. “Strengthening of RC members with near-surface mounted CFRP rods”, Composite structures”, Vol. (91), pp. 138-147. (2009).

[13] Almusallam, T., H., Elsanadedy, H., M., Al-Salloum, Y., A. and Alsayed, S., H. “Experimental and numerical investigation for the flexural strengthening of RC beams using near-surface mounted steel or GFRP bars”, Construction and building materials, Vol. (40), pp.145-161. (2013).

[14] ACI Committee 318 “Building code requirements for structural concrete and commentary. ACI318-11”, American concrete institute, Detroit, MI, USA.  (2011).

[15] ACI Committee 440 “Guide for the Design and Construction of Structural Concrete reinforced with FRP bars. ACI440.IR-06-11”, American concrete institute Detroit, MI, USA. (2006).

[16] Abdullah, A., H., “Flexural Strengthening of RC Members with Near Surface Mounted FRP Reinforcement”, MSc Thesis, Civil Engineering Department, University of Nottingham, Nottingham. (2013).

[17] Nanni, A. “North American design guidelines for concrete reinforcement and strengthening using FRP: principles, applications and unresolved issues”, Center for Infrastructure Engineering Studies, University of Missouri–Rolla, Rolla, USA. (2003).

[18] Parretti, R. and Nanni, A. “Strengthening of RC Members Using Near-SurfaceMounted FRP Composites: Design Overview”, Advances in Structural Engineering, Vol. (7), No. 5. (2004).

[19] Delorenzis, L., Nanni, A. Bond between Near-Surface Mounted FRP Rods and Concrete in Structural Strengthening”, ACI Structures Journal, Vol. (99), No. 2, pp. 123-133. (2002).

[20] Hawileh, R., A. “Nonlinear finite element modelling of RC beams strengthened with NSM FRP rods”, Construction and building materials, Vol. (27), pp. 461-471. (2012).

[21] Kotynia, R. “Bond between FRP and concrete in reinforced concrete beams strengthened with near surface mounted and externally bounded reinforcement”, Construction and building materials, Vol. (32), pp. 41-54. (2012).

[22] Teng, J.G., Delorenzis, L., Wang, B., Li, R., Wong, T. N. and Lam, L. “Debonding failures of RC beams strengthened with near surface mounted CFRP strips”, Journal of composites for construction, Vol. (10), No. 2, pp. 92-105. (2006).

[23] Hassan, T. and Rizkalla, S. “Investigation of bond in concrete structures strengthened with near surface mounted carbon fibre reinforced polymer strips”, Journal of composites for construction,Vol. (7), No. 3, pp. 248-257. (2003).