Browse > Article
http://dx.doi.org/10.12989/sem.2018.67.1.045

Experimental investigation on optimal shear strengthening of RC beams using NSM GFRP bars  

Ramezanpour, M. (Department of Civil Engineering, Yazd University)
Morshed, R. (Department of Civil Engineering, Yazd University)
Eslami, A. (Department of Civil Engineering, Yazd University)
Publication Information
Structural Engineering and Mechanics / v.67, no.1, 2018 , pp. 45-52 More about this Journal
Abstract
Several techniques have been developed for shear strengthening of reinforced concrete (RC) members by using fiber reinforced polymer (FRP) composites. However, debonding of FRP retrofits from concrete substrate still deemed as a challenging concern in their application which needs to be scrutinized in details. As a result, this paper reports on the results of an experimental investigation on shear strengthening of RC beams using near surface mounted (NSM) FRP reinforcing bars. The main objective of the experimentation was increasing the efficiency of shear retrofits by precluding/postponing the premature debonding failure. The experimental program was comprised of six shear deficient RC beams. The test parameters include the FRP rebar spacing, inclination angle, and groove shape. Also, an innovative modification was introduced to the conventional NSM technique and its efficiency was evaluated by experimental observation and measurement. The results testified the efficiency of glass FRP (GFRP) rebars in increasing the shear strength of the test specimens retrofitted using conventional NSM technique. However, debonding of FRP bars impeded exploiting all retrofitting advantages and induced a premature shear failure. On the contrary, application of the proposed modified NSM (MNSM) technique was not only capable of preventing the premature debonding of FRP bars, but also could replace the failure mode of specimen from the brittle shear to a ductile flexural failure which is more desirable.
Keywords
RC beam; shear strengthening; GFRP rebars; debonding; NSM; modified NSM;
Citations & Related Records
Times Cited By KSCI : 4  (Citation Analysis)
연도 인용수 순위
1 Dalalbashi, A., Eslami, A. and Ronagh, H.R. (2013), "Numerical investigation on the hysteretic behavior of RC joints retrofitted with different CFRP configurations", J. Compos. Constr., 17(3), 371-382.   DOI
2 De Lorenzis, L. and Nanni, A. (2001), "Shear strengthening of reinforced concrete beams with near-surface mounted fiberreinforced polymer rods", ACI Struct. J., 98(1), 60-68.
3 Deng, J., Airong, L., Peiyan, H. and Xiaohong, Z. (2016), "Interfacial mechanical behaviors of RC beams strengthened with FRP", Struct. Eng. Mech., 58(3), 577-596.   DOI
4 Dias, S.J. and Barros, J.A. (2013), "Shear strengthening of RC beams with NSM CFRP laminates: Experimental research and analytical formulation", Compos. Struct., 99, 477-490.   DOI
5 El-Mihilmy, M.T. and Tedesco, J.W. (2000), "Analysis of reinforced concrete beams strengthened with FRP laminates", J. Struct. Eng., 126(6), 684-691.   DOI
6 Eslami, A. and Ronagh, H.R. (2014), "Experimental investigation of an appropriate anchorage system for flange-bonded carbon fiber-reinforced polymers in retrofitted RC beam-column joints", J. Compos. Constr., 18(4), 04013056.   DOI
7 Jalali, M., Sharbatdar, M.K., Chen, J.F. and Alaee, F.J. (2012), "Shear strengthening of RC beams using innovative manually made NSM FRP bars", Constr. Build. Mater., 36, 990-1000.   DOI
8 Khalifa, A., Gold, W.J., Nanni, A. and Mi, A.A. (1998), "Contribution of externally bonded FRP to shear capacity of RC flexural members", J. Compos. Constr., 2(4), 195-202.   DOI
9 Kocak, A. (2015), "Earthquake performance of FRP retrofitting of short columns around band-type windows", Struct. Eng. Mech., 53(1), 1-16.   DOI
10 ACI Committee 440 (2008), Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures (ACI 440.2R-08), Farmington Hills, Michigan, U.S.A.
11 Anil, O., Belgin, C.M. and Kara, M.E. (2010), "Experimental investigation on CFRP-to-concrete bonded joints across crack", Struct. Eng. Mech., 35(1), 1-18.   DOI
12 ASTM A370 (2017), Standard Test Methods and Definitions for Mechanical Testing of Steel Products, American Society for Testing and Materials, West Conshohocken, Pennsylvania, U.S.A.
13 Chajes, M.J., Thomson, T.A., Januszka, T.F. and Finch, W.W. (1994), "Flexural strengthening of concrete beams using externally bonded composite materials", Constr. Build. Mater., 8(3), 191-201.   DOI
14 Kocak, A., Onal, M.M. and Sonmez, K. (2007), "Repairing and strengthening methods for RC structural members", Proceedings of the 6th International Conference on Fracture Mechanics of Concrete and Concrete Structures, Volume 2: Design, Assessment and Retrofitting of RC Structures, Catania, Italy.
15 Mahini, S.S. and Ronagh, H.R. (2011), "Web-bonded FRPs for relocation of plastic hinges away from the column face in exterior RC joints", Compos. Struct., 93(10), 2460-2472.   DOI
16 Baji, H., Eslami, A. and Ronagh, H.R. (2015), "Development of a nonlinear FE modelling approach for FRP-strengthened RC beam-column connections", Struct., 3, 272-281.   DOI
17 Barros, J.A. and Dias, S.J. (2003), "Shear strengthening of reinforced concrete beams with laminate strips of CFRP", Proceedings of the International Conference Composites in Constructions.
18 Bianco, V., Monti, G. and Barros, J.A. (2014), "Design formula to evaluate the NSM FRP strips shear strength contribution to a RC beam", Compos. Part B: Eng., 56, 960-971.   DOI
19 CSA (2012), Design and Construction of Building Structures with Fibre-Reinforced Polymers, CSA-S806-12, Canadian Standards Association, Mississauga, Ontario, Canada.
20 Dalalbashi, A., Eslami, A. and Ronagh, H.R. (2012), "Plastic hinge relocation in RC joints as an alternative method of retrofitting using FRP", Compos. Struct., 94(8), 2433-2439.   DOI
21 Onal, M.M., Zengin, B., Kocak, A. and Doran, B. (2014), "An experimental investigation on flexural behavior of RC beams strengthened with different techniques", KSCE J. Civil Eng., 18(7), 2162-2169.   DOI
22 Mahini, S.S. and Ronagh, H.R. (2010), "Strength and ductility of FRP web-bonded RC beams for the assessment of retrofitted beam-column joints", Compos. Struct., 92(6), 1325-1332.   DOI
23 Mosallam, A.S. and Banerjee, S. (2007), "Shear enhancement of reinforced concrete beams strengthened with FRP composite laminates", Compos. Part B-Eng., 38(5-6), 781-793.   DOI
24 Mostofinejad, D. and Mahmoudabadi, E. (2010), "Grooving as alternative method of surface preparation to postpone debonding of FRP laminates in concrete beams", J. Compos. Constr., 14(6), 804-811.   DOI
25 Rizzo, A. and De Lorenzis, L. (2009), "Behavior and capacity of RC beams strengthened in shear with NSM FRP reinforcement", Constr. Build. Mater., 23(4), 1555-1567.   DOI
26 Teng, J., Huang, Y., Lam, L. and Ye, L. (2007), "Theoretical model for fiber-reinforced polymer-confined concrete", J. Compos. Constr., 11(2), 201-210.   DOI