Bundling Effect on Bond and Development Length of Sand-Coated GFRP Bars
Publication: Journal of Composites for Construction
Volume 28, Issue 5
Abstract
One of the gaps in the new Building Code Requirements for Structural Concrete Reinforced with Glass Fiber–Reinforced Polymer (GFRP) Bars is design provisions for bundled GFRP bars. This study aims at establishing the bundling factor for the development length (Ld) of sand-coated GFRP bars embedded into normal strength concrete in bundles of two and three. A total of 12 notched beams were tested in flexure with spans ranging from 1 to 3 m, where the bars and surrounding concrete are under realistic tensile stress as opposed to pull-out tests. The embedment length (Le) of the bars varied from 17 to 87 times bar diameter (db), to establish a correlation with maximum tensile stress attained, thereby enabling calculating Ld. For each bundled arrangement, counterpart beams with spaced bars were also tested for comparison. It was found that bundling bars reduced the maximum attained longitudinal tensile stress at bond failure by 18%–30% for two bars and 20%–36% for three bars, within the studied Le range of 17–87db. At the full design tensile strength (ffu), Ld of bundles of two and three bars was 1.4 and 1.5 times larger, respectively, than spaced bars. As the tensile stress ratio (ff/ffu) reduced from 1.0 to 0.34 (as in compression-controlled failure), Ld of bundles increased up to 1.9 and 2.5 times the spaced bars, respectively. An expression for this variable bundling factor is proposed.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article.
Acknowledgments
The authors wish to acknowledge the financial support of the Natural Engineering and Research Council of Canada (NSERC) and the in-kind contribution of V-Rod and Pultrall Inc.
Notation
The following symbols are used in this paper:
- A
- constant;
- Ab
- cross-sectional area of the GFRP bar;
- a
- shear span of the beam;
- B
- constant;
- C
- cover to the center of the bar;
- CE
- environmental reduction factor;
- db
- bar diameter;
- equivalent GFRP bundle diameter;
- concrete compressive strength at 28 days typically, but here at time of test;
- ff
- longitudinal GFRP bar stress at peak lad P;
- ffu
- guaranteed ultimate tensile strength;
- ffr
- design tensile strength (ffu) for tension controlled failure or the GFRP tensile stress corresponding to concrete crushing for compression controlled failure;
- ffu
- maximum possible design tensile strength = ;
- guaranteed tensile strength reported by the manufacturer;
- K
- correction factor;
- Ld
- development length;
- Ld,spaced
- development length of spaced bars;
- Ld,bundled
- development length of bundled bars;
- Le
- embedment length;
- nb
- number of bars in a bundle;
- P
- peak load of the beam at splitting bond failure;
- u
- average bond stress at peak load P; and
- y
- vertical distance between the tension force (centroid of GFRP bar or bundle of bars) and the compression force (centroid of the steel roller).
References
Achillides, Z., and K. Pilakoutas. 2004. “Bond behavior of fiber reinforced polymer bars under direct pullout conditions.” J. Compos. Constr. 8 (2): 173–181. https://doi.org/10.1061/(ASCE)1090-0268(2004)8:2(173).
ACI (American Concrete Institute). 2015. Guide for the design and construction of structural concrete reinforced with FRP bars. ACI PCR-440.1-15. Farmington Hills, MI: ACI.
ACI (American Concrete Institute). 2022. Building code requirements for structural concrete reinforced with glass fiber-reinforced polymer (GFRP) bars. ACI440.11-22. Farmington Hills, MI: ACI.
Asadian, A., A. Eslami, A. S. Farghaly, and B. Benmokrane. 2019. “Splice strength of staggered and non-staggered bundled glass fiber-reinforced polymer reinforcing bars in concrete.” ACI Struct. J. 116: 129–142.
Benmokrane, B., O. Chaallal, and R. Masmoudi. 1995. “Glass fibre reinforced plastic (GFRP) rebars for concrete structures.” Constr. Build. Mater. 9 (6): 353–364. https://doi.org/10.1016/0950-0618(95)00048-8.
Benmokrane, B., B. Tighiouart, and O. Chaallal. 1996. “Bond strength and load distribution of composite GFRP reinforcing bars in concrete.” ACI Mater. J. 93 (3): 254–259. https://doi.org/10.14359/9810.
British Standards. 2005. Steel for the reinforcement of concrete — Weldable reinforcing steel. General BS EN 10080:2005. London, UK: British Standards.
CEN (European Committee for Standardization). 2004. Design of concrete structures - part 1-1 : General rules and rules for buildings. Eurocode 2. Brussels, Belgium: CEN.
CSA (Canadian Standard Association). 2021. Design and construction of building structures with fibre-reinforced polymers. CSA S806:12 (R2021). Rexdale, ON: CSA.
Darwin, D., J. Zuo, M. L. Tholen, and E. K. Idun. 1996. “Development length criteria for conventional and high relative rib area reinforcing bars.” ACI Struct. J. 93 (3): 347–359.
Ehsani, M. R., H. Saadatmanesh, and S. Tao. 1997. “Bond behavior of deformed GFRP rebars.” J. Compos. Mater. 31 (14): 1413–1430. https://doi.org/10.1177/002199839703101404.
Jirsa, J. O., W. Chen, D. B. Grant, and R. Elizondo. 1995. Development of bundled reinforcing steel. Austin, TX: Univ. of Texas.
Mermigas, K. K., R. Mihaljevic, and W. Kenedi. 2018. “Evolution of bridge practices in Ontario, Canada.” In Proc., of the Structures Session of the 2018 Conf. of the Transportation Association of Canada, 1–18. Ottawa, ON: Transportation Association of Canada.
Metelli, G., J. Cairns, A. Conforti, and G. A. Plizzari. 2021. “Local bond behavior of bundled bars: Experimental investigation.” Struct. Concr. 22 (4): 2322–2337. https://doi.org/10.1002/suco.202000576.
Nanni, A. 1993. “Flexural behavior and design of RC members using FRP reinforcement.” J. Struct. Eng. 119 (11): 3344–3359. https://doi.org/10.1061/(ASCE)0733-9445(1993)119:11(3344).
Olanike, A. O. 2014. “A comparative analysis of modulus of rupture and splitting tensile strength of recycled aggregate concrete.” Am. J. Eng. Res. 3: 141–147.
RILEM. 1994. Recommendations for the testing and use of construction materials. London: E & FN Spon.
Salem, R. M. 1996. “Strength and durability characteristics of recycled aggregate concrete.” Ph.D. thesis, Dept. of Civil Engineering, Univ. of Tennessee.
Troxell, G. E., H. E. Davis, and J. W. Kelly. 1968. Composition and properties of concrete. New York: McGraw-Hill.
Wambeke, B. W., and C. K. Shield. 2006. “Development length of glass fiber-reinforced polymer bars in concrete.” ACI Struct. J. 103 (1): 11–17.
Yan, F., Z. Lin, and M. Yang. 2016. “Bond mechanism and bond strength of GFRP bars to concrete: A review.” Composites, Part B 98: 56–69. https://doi.org/10.1016/j.compositesb.2016.04.068.
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Published In
Journal of Composites for Construction
Volume 28 • Issue 5 • October 2024
Copyright
© 2024 American Society of Civil Engineers.
History
Received: Sep 16, 2023
Accepted: Apr 3, 2024
Published online: Jun 28, 2024
Published in print: Oct 1, 2024
Discussion open until: Nov 28, 2024
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