Experimental Investigation on the Behavior of Reinforced Concrete Beams Retrofitted with NSM-SMA/FRP

Document Type : Research Article


1 M.Sc, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

2 Professor, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

3 Ph.D. Student, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran


Re-centering is an exclusive characteristic of superelastic Shape Memory Alloys (SMAs) which can be used in manufacturing and retrofitting of reinforced concrete elements. Reinforced concrete beams retrofitted with SMA bars have more ductility and higher energy dissipation compared to conventional RC beams. Furthermore, these beams experience less damage in consecutive loading-unloading cycles. The current research aims to investigate the behavior of reinforced concrete beams retrofitted with SMA bars using Near-Surface Mounted (NSM) flexural retrofitting method. Eleven RC beam specimens with the cross section of 200*150 mm and length of 1150 mm were cast. Three of the specimens had no external strengthening, four of them were retrofitted with SMA bars and other four beams were retrofitted with GFRP reinforcements. The specimens were subjected to three-point bending test under either monastic or loading-unloading. Different parameters including load-carrying capacity, energy dissipation, deformation recovery and reduction capability of crack width were investigated. The results showed that RC beams retrofitted with SMA bars had more mid-span deflection and higher energy dissipation compared to other specimens under monotonic loading. Moreover, under loading-unloading, RC beams retrofitted with SMA bars method experienced less damage.


Main Subjects

[1]  R.Y. Huang, I.S. Mao, H.K. Lee, Exploring the deterioration factors of RC bridge decks: a rough set approach, Computer‐Aided Civil and Infrastructure Engineering, 25(7) (2010) 517-529.
[2]  L.C. HOLLAWAY, Case studies, in: Strengthening and Rehabilitation of Civil Infrastructures Using Fibre-Reinforced Polymer (FRP) Composites, Elsevier, 2008, pp. 352-385.
[3]  J. Teng, J.-F. Chen, S.T. Smith, L. Lam, FRP: strengthened RC structures, Frontiers in Physics, (2002) 266.
[4]  R. Seracino, M. Raizal Saifulnaz, D.  Oehlers,  Generic debonding resistance of EB and NSM plate-to-concrete joints, Journal of Composites for Construction, 11(1) (2007) 62-70.
[5]  I. Liu, D. Oehlers, R. Seracino, Tests on the ductility of reinforced concrete beams retrofitted with FRP and steel near-surface mounted plates, Journal of Composites for Construction, 10(2) (2006) 106-114.
[6]  J. Bonacci, M. Maalej, Behavioral trends of RC beams strengthened with externally bonded FRP, Journal of Composites for Construction, 5(2) (2001) 102-113.
[7]  L. Bizindavyi, K. Neale, Transfer lengths and bond strengths for composites bonded to concrete, Journal of composites for construction, 3(4) (1999) 153-160.
[8]  J. Sabzi, M.R. Esfahani, Flexural behavior of RC beams strengthened by CFRP sheets in the beams with low and high reinforcement ratios, Amirkabir J. Civil Eng., 50 (5) (2018) 907-918.
[9]  J. Sabzi, M.R. Esfahani, Effects of tensile steel bars arrangement on concrete cover separation of RC beams strengthened by CFRP sheets, Construction and Building Materials, 162 (2018) 470-479.
[10] F. Ceroni, M. Pecce, A. Bilotta, E. Nigro, Bond behavior of FRP NSM systems in concrete elements, Composites Part B: Engineering, 43(2) (2012) 99-109.
[11]   F. Oudah, R. El-Hacha, Fatigue behavior of RC beams strengthened with prestressed NSM CFRP rods, Composite Structures, 94(4) (2012) 1333-1342.
[12] R. El-Hacha, S.H. Rizkalla, Near-surface-mounted fiber-reinforced polymer reinforcements for flexural strengthening of concrete structures, Structural Journal, 101(5) (2004) 717-726.
[13] R.  Kotynia,  Bond   between   FRP   and   concrete  in reinforced concrete  beams  strengthened  with near surface mounted and externally bonded reinforcement, Construction and Building Materials, 32 (2012) 41-54.
[14]  L.D. Lorenzis, A. Nanni, Characterization of FRP rods as near-surface mounted reinforcement, Journal of Composites for Construction, 5(2) (2001) 114-121.
[15]  S.M. Soliman, E. El-Salakawy, B. Benmokrane, Bond performance of near-surface-mounted FRP bars, Journal of Composites for Construction, 15(1) (2010) 103-111.
[16]  I.A. Sharaky, L. Torres, M. Baena, I. Vilanova, Effect of different material and construction details on the bond behaviour of NSM FRP bars in concrete, Construction and Building Materials, 38 (2013) 890- 902.
[17]  S.M. Daghash, O.E. Ozbulut, Bond–slip behavior of superelastic shape memory alloys for near-surface- mounted strengthening applications, Smart Materials and Structures, 26(3) (2017) 035020.
[18]  R. El-Hacha, M. Gaafar, Flexural strengthening of reinforced concrete beams using prestressed, near- surfacemounted CFRP bars, PCI journal, 56(4) (2011).
[19]  C. Czaderski, M. Shahverdi, R. Brönnimann, C. Leinenbach, M. Motavalli, Feasibility  of  iron-  based shape memory alloy strips for prestressed strengthening of concrete structures, Construction and Building Materials, 56 (2014) 94-105.
[20]  S. Al-Obaidi, Behavior of reinforced concrete beams retrofitted in flexure using CFRP-NSM technique, (2015).
[21]  A. Abdulridha, D. Palermo, S. Foo, F.J. Vecchio, Behavior and modeling of superelastic shape memory alloy reinforced concrete beams, Engineering Structures, 49 (2013) 893-904.
[22]H. Li,  Z.-q.  Liu,  J.-p.  Ou,  Experimental  study  of a simple reinforced concrete beam temporarily strengthened by SMA wires followed by permanent strengthening with CFRP plates, Engineering Structures, 30(3) (2008) 716-723.
[23]  N. Wierschem, B. Andrawes, Superelastic SMA–FRP composite reinforcement for concrete structures, Smart materials and structures, 19(2) (2010) 025011.
[24]  C. Czaderski, B. Hahnebach, M. Motavalli, RC beam with variable stiffness and strength, Construction and Building Materials, 20(9) (2006) 824-833.
[25]  K. Moser, A. Bergamini, R. Christen, C. Czaderski, Feasibility of concrete prestressed by shape memory alloy short fibers, Materials and Structures, 38(5) (2005) 593-600.
[26]  O. Ozbulut, S. Hurlebaus, Neuro-fuzzy modeling of temperature-and strain-rate-dependent behavior of NiTi shape memory alloys for seismic applications, Journal of Intelligent Material Systems and Structures, 21(8) (2010) 837-849.
[27]  ACI Committee 318, Building Code Requirements for Structural Concrete and Commentary, American Concrete Institute, Farmington Hills, 2014.
[28]  ACI 440.2R-17. "Guide for the Design and Construction of Externally Bonded Frp Systems for Strengthening Concrete Structures." Reported by ACI Committee 440.2017 (2017).
[29]  D. Mostofinejad, A. Moghaddas,  Bond  efficiency  of EBR and EBROG methods in different flexural failure mechanisms of FRP strengthened RC beams, Construction and Building Materials, 54 (2014) 605- 614.
[30]  S.M. Soliman, E. El-Salakawy, B. Benmokrane, Flexural behaviour of concrete beams strengthened with near surface mounted fibre reinforced polymer bars, Canadian Journal of Civil Engineering, 37(10) (2010) 1371-1382.