Experimental Investigation of Concrete Beams Reinforced with Glass Fiber–Reinforced Polymer Bars
Publication: Journal of Composites for Construction
Volume 26, Issue 5
Abstract
Concrete beams reinforced in shear and flexure with linear elastic and brittle glass fiber–reinforced polymer (GFRP) bars show differences in behavior when compared with the traditional steel-reinforced concrete beams. The flexural design of these beams follows similar principles as the design of steel-reinforced concrete members, except that the cross section is over-reinforced to compensate for the lack of reinforcement ductility. GFRP-reinforced beams are designed in shear using semiempirical modifications to the design equations for steel-reinforced concrete. The modified equations have not been well studied for beams with high shear span to depth (a/d) ratios. The presented research program is composed of three-point bending tests of ten GFRP-reinforced concrete beams, with a/d slenderness ratios from 4.5 to 10.5 with constant flexural reinforcement and varied shear reinforcing. The observed mode of failure transitioned from shear to flexure-controlled with increasing specimen slenderness and increased shear reinforcing. All failures were controlled by concrete behavior, either in tension for beams without shear reinforcement or compression for beams with shear reinforcement. The inclusion of GFRP stirrups in the beams prevented brittle failures by providing confinement to concrete. Comparisons with the current design rules showed good agreement with experimental results. However, the relative contribution of concrete and reinforcement to shear-carrying capacities differed in the code predictions from results derived from measured strains.
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Acknowledgments
The authors acknowledge the financial contribution of the Natural Sciences and Engineering Council of Canada (NSERC) and the Ministry of Transportation of Ontario (MTO) for their financial support of this research program. The authors also extend their thanks to Schoeck/Fiberline for their contributions of longitudinal reinforcement and to B&BFRP composites for the donation of stirrups.
Notation
The following symbols are used in this paper:
- a
- shear span, distance from support to point of load application;
- a/d
- ratio of shear span to the depth of longitudinal reinforcement;
- AR
- sectional area of longitudinal reinforcement;
- AV, AfV
- area of shear reinforcement within a single spacing;
- bw
- width of the concrete compressive zone (equivalent for rectangular sections);
- d
- depth from the extreme compression fiber to the centroid of the tensile longitudinal reinforcement;
- dv
- effective shear depth;
- ER, EF
- axial stiffness of longitudinal reinforcement;
- specified concrete compressive strength;
- ffu
- ultimate allowable stress in the transverse GFRP reinforcement;
- fy
- yield strength of steel;
- k
- ratio of depth of neutral axis to reinforcement depth;
- km
- modification factor for moment interaction;
- kr
- modification factor for the stiffness of longitudinal reinforcement;
- Mf
- factored applied moment;
- Mr
- flexural resistance of a member;
- s
- spacing of transverse reinforcement;
- Vc
- concrete contribution to the overall shear resistance of a beam;
- Vf
- factored applied shear;
- Vr
- shear resistance of a beam;
- VsF
- transverse FRP reinforcement contribution to the overall shear resistance of a beam;
- Vss
- transverse steel reinforcement contribution to the overall shear resistance of a beam;
- λ
- factor to account for the effect of concrete density of shear resistance;
- ϕc
- material resistance factor for concrete, taken as 1 for this research;
- ϕF
- material resistance factor for FRP, taken as 1 for this research;
- ρFw
- longitudinal reinforcement ratio; and
- θ
- angle of inclination of the principal compressive stress to the longitudinal axis of the member.
References
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Published In
Journal of Composites for Construction
Volume 26 • Issue 5 • October 2022
Copyright
© 2022 American Society of Civil Engineers.
History
Received: Aug 12, 2021
Accepted: May 26, 2022
Published online: Jul 21, 2022
Published in print: Oct 1, 2022
Discussion open until: Dec 21, 2022
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Cited by
- R. Barrage, M.A. Polak, Flexural and shear behaviours of GFRP-reinforced concrete beams based on nonlinear finite element studies, Canadian Journal of Civil Engineering, 10.1139/cjce-2022-0179, 50, 2, (90-101), (2023).