Title:
Variable Bond of Glass Fiber-Reinforced Polymer Bars for Reinforced Concrete Beams under Arch and Beam Actions
Author(s):
Yail J. Kim and Ali Alatify
Publication:
Structural Journal
Volume:
123
Issue:
1
Appears on pages(s):
75-88
Keywords:
bond length; fiber-reinforced polymer (FRP); partial bond; reinforcement
DOI:
10.14359/51749131
Date:
1/1/2026
Abstract:
This paper presents the implications of variable bond for the behavior of concrete beams with glass fiber-reinforced polymer (GFRP) bars alongside shear-span-dependent load-bearing mechanisms. Experimental programs are undertaken to examine element- and structural-level responses incorporating fully and partially bonded reinforcing bars, which are intended to represent sequential bond damage. Conforming to published literature, three shear span-depth ratios (av/d) are taken into account: arch action (av/d < 2.0), beam action (3.5 ≤ av/d), and a transition from arch to beam actions (2.0 ≤ av/d < 3.5). When sufficient bond is provided for the element-level testing (over 75% of 5db, where db is the reinforcing bar diameter), the interfacial failure of GFRP is brittle against a concrete substrate. An increase in the av/d from 1.5 to 3.7, aligning with a change from arch action to beam action, decreases the load-carrying capacity of the beams by up to 40.2%, and the slippage of the partially bonded reinforcing bars dominates their flexural stiffness. Compared with the case of the beams under beam action, the mutual dependency of the bond length and shear span is apparent for those under arch action. As far as failure characteristics are concerned, the absence of bond in the arch-action beam prompts crack localization; by contrast, partially bonded ones demonstrate diagonal tension cracking adjacent to the compression strut that transmits applied load to the nearby support. The developmental process of reinforcing bar stress is dependent upon the av/d and, in terms of using the strength of GFRP, beam action is favorable relative to arch action. Analytical modeling suggests design recommendations, including degradation factors for the calculation of reinforcing bar stresses with bond damage when subjected to arch and beam actions.
Related References:
1. Eligehausen, R.; Popov, E. P.; and Bertero, V. V., “Local Bond Stress-Slip Relationships of Deformed Bars under Generalized Excitations,” Report No. UCB/EERC-83/23, Earthquake Engineering Research Center, University of California, Berkeley, Berkeley, CA, 1983.
2. Wight, J. K., Reinforced Concrete: Mechanics and Design, Pearson, Hoboken, NJ, 2022.
3. Zhang, N.; Gu, Q.; Wu, Y.; and Xue, X., “Refined Peridynamic Modeling of Bond-Slip Behaviors between Ribbed Steel Rebar and Concrete in Pull-Out Tests,” Journal of Structural Engineering, ASCE, V. 148, No. 12, 2022, p. 04022197. doi: 10.1061/(ASCE)ST.1943-541X.0003396
4. Choi, O. C., and Choi, H., “Bearing Angle Model for Bond of Reinforcing Bars in Concrete,” ACI Structural Journal, V. 114, No. 1, Jan. 2017, pp. 245-253.
5. Ruiz, M. F.; Muttoni, A.; and Gambarova, P. G., “Analytical Modeling of the Pre- and Postyield Behavior of Bond in Reinforced Concrete,” Journal of Structural Engineering, ASCE, V. 133, No. 10, 2007, pp. 1364-1372. doi: 10.1061/(ASCE)0733-9445(2007)133:10(1364)
6. Fu, C.; Fang, D.; Ye, H.; Huang, L.; and Wang, J., “Bond Degradation of Non-Uniformly Corroded Steel Rebars in Concrete,” Engineering Structures, V. 226, 2021, p. 111392. doi: 10.1016/j.engstruct.2020.111392
7. Nawy, E. G., Reinforced Concrete: A Fundamental Approach, Pearson, Hoboken, NJ, 2008.
8. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19) (Reapproved 2022),” American Concrete Institute, Farmington Hills, MI, 2019, 624 pp.
9. Regan, P., “Aspects of Diagonal Tension in Reinforced Concrete,” Structural Concrete, V. 1, No. 3, 2000, pp. 119-132. doi: 10.1680/stco.2000.1.3.119
10. Issa, M. A.; Ovitigala, T.; and Ibrahim, M., “Shear Behavior of Basalt Fiber Reinforced Concrete Beams with and without Basalt FRP Stirrups,” Journal of Composites for Construction, ASCE, V. 20, No. 4, 2016, p. 04015083. doi: 10.1061/(ASCE)CC.1943-5614.0000638
11. Ridha, M. M. S.; Sarsam, K. F.; and Al-Shaarbaf, I. A. S., “Experimental Study and Shear Strength Prediction for Reactive Powder Concrete Beams,” Case Studies in Construction Materials, V. 8, 2018, pp. 434-446. doi: 10.1016/j.cscm.2018.03.002
12. ACI Committee 440, “Guide for the Design and Construction of Structural Concrete Reinforced with Fiber-Reinforced Polymer (FRP) Bars (ACI 440.1R-15),” American Concrete Institute, Farmington Hills, MI, 2015, 88 pp.
13. ACI Committee 440, “Building Code Requirements for Structural Concrete Reinforced with Glass Fiber-Reinforced Polymer (GFRP) Bars—Code and Commentary (ACI CODE-440.11-22),” American Concrete Institute, Farmington Hills, MI, 2022, 260 pp.
14. Tekle, B. H.; Khennane, A.; and Kayali, O., “Bond Properties of Sand-Coated GFRP Bars with Fly Ash-Based Geopolymer Concrete,” Journal of Composites for Construction, ASCE, V. 20, No. 5, 2016, p. 04016025. doi: 10.1061/(ASCE)CC.1943-5614.0000685
15. Kazemi, H.; Yekrangnia, M.; Shakiba, M.; Bazli, M.; and Oskouei, A. V., “Bond-Slip Behaviour between GFRP/Steel Bars and Seawater Concrete after Exposure to Environmental Conditions,” Engineering Structures, V. 268, 2022, p. 114796. doi: 10.1016/j.engstruct.2022.114796
16. Hosseini, S. A.; Farghaly, A. S.; Eslami, A.; Nanni, A.; and Benmokrane, B., “Bond Behaviour of Lap Spliced GFRP Bars in Concrete Members: A State-of-the-Art Review and Design Recommendations,” Construction and Building Materials, V. 411, 2024, p. 134714. doi: 10.1016/j.conbuildmat.2023.134714
17. ASTM C39/C39M-21, “Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens,” ASTM International, West Conshohocken, PA, 2021.
18. ACI Committee 440, “Guide Test Methods for Fiber-Reinforced Polymer (FRP) Composites for Reinforcing or Strengthening Concrete and Masonry Structures (ACI 440.3R-12),” American Concrete Institute, Farmington Hills, MI, 2012, 23 pp.
19. Podgorniak-Stanik, B. A., “The Influence of Concrete Strength, Distribution of Longitudinal Reinforcement, Amount of Transverse Reinforcement and Member Size on Shear Strength of Reinforced Concrete Members,” MS thesis, University of Toronto, Toronto, ON, Canada, 1998.
20. Lundgren, K.; Robuschi, S.; and Zandi, K., “Methodology for Testing Rebar-Concrete Bond in Specimens from Decommissioned Structures,” International Journal of Concrete Structures and Materials, V. 13, No. 1, 2019, p. 38 doi: 10.1186/s40069-019-0350-3
21. Suparp, S.; Khan, I.; Ejaz, A.; Khan, K.; Weesakul, U.; Hussain, Q.; and Saingam, P., “Behavior of Non-Prismatic RC Beams with Conventional Steel and Green GFRP Rebars for Sustainable Infrastructure,” Scientific Reports, V. 13, No. 1, 2023, p. 15733. doi: 10.1038/s41598-023-41467-w
22. MacGregor, J. G., Reinforced Concrete: Mechanics and Design, Prentice Hall, Upper Saddle River, NJ, 1997.
23. Bielak, J., and Hegger, J., “Enhancing Shear Capacity of Thin Slabs with CFRP Shear Reinforcement: Experimental Study,” Structural Concrete, V. 22, No. 5, 2021, pp. 3057-3073. doi: 10.1002/suco.202100325
24. Young, H. D., and Freedman, R. A., University Physics, Addison-Wesley Publishing, Reading, MA, 1996.
25. Saliba, J., and Mezhoud, D., “Monitoring of Steel-Concrete Bond with the Acoustic Emission Technique,” Theoretical and Applied Fracture Mechanics, V. 100, 2019, pp. 416-425. doi: 10.1016/j.tafmec.2019.01.034
26. Bažant, Z. P.; Le, J.-L.; and Salviato, M., Quasibrittle Fracture Mechanics and Size Effect: A First Course, Oxford University Press, Oxford, UK, 2021.
27. Irshidat, M. R., “Improved Bond Behavior between FRP Reinforcing Bars and Concrete with Carbon Nanotubes,” Construction and Building Materials, V. 257, 2020, p. 119562. doi: 10.1016/j.conbuildmat.2020.119562
28. Tan, K. H., and Cheng, G. H., “Size Effect on Shear Strength of Deep Beams: Investigating with Strut-and-Tie Model,” Journal of Structural Engineering, ASCE, V. 132, No. 5, 2006, pp. 673-685. doi: 10.1061/(ASCE)0733-9445(2006)132:5(673)
29. Trandafir, A. N.; Ernens, G.; and Mihaylov, B. I., “Crack-Based Evaluation of Internally FRP-Reinforced Concrete Deep Beams without Shear Reinforcement,” Journal of Composites for Construction, ASCE, V. 27, No. 5, 2023, p. 04023047. doi: 10.1061/JCCOF2.CCENG-4232
30. Chen, H.-R. R., and Choi, J.-H., “Analysis of Shrinkage and Thermal Stresses in Concrete Slabs Reinforced with GFRP Rebars,” Journal of Materials in Civil Engineering, ASCE, V. 23, No. 5, 2011, pp. 612-627. doi: 10.1061/(ASCE)MT.1943-5533.0000216
31. Okeil, A.; El-Tawil, S.; and Shahawy, M., “Flexural Reliability of Reinforced Concrete Bridge Girders Strengthened with Carbon Fiber-Reinforced Polymer Laminates,” Journal of Bridge Engineering, ASCE, V. 7, No. 5, 2002, pp. 290-299. doi: 10.1061/(ASCE)1084-0702(2002)7:5(290)
32. Nowak, A. S., and Collins, K. R., Reliability of Structures, second edition, CRC Press, Boca Raton, FL, 2013.
33. Baji, H., and Ronagh, H. R., “Reliability-Based Study on Ductility Measures of Reinforced Concrete Beams in ACI 318,” ACI Structural Journal, V. 113, No. 2, Mar.-Apr. 2016, pp. 373-382. doi: 10.14359/51688201
34. Nasrollahzadeh, K., and Aghamohammadi, R., “Reliability Analysis of Shear Strength Provisions for FRP-Reinforced Concrete Beams,” Engineering Structures, V. 176, 2018, pp. 785-800. doi: 10.1016/j.engstruct.2018.09.016
35. Ribeiro, S. E. C., and Diniz, S. M. C., “Reliability-Based Design Recommendations for FRP-Reinforced Concrete Beams,” Engineering Structures, V. 52, 2013, pp. 273-283. doi: 10.1016/j.engstruct.2013.02.026
36. ACA, “Notes on ACI 318-05 Building Code Requirements for Structural Concrete with Design Applications,” American Cement Association, Skokie, IL, 2005.