Flexural Behavior and Design of Ultrahigh-Performance Concrete Beams Reinforced with GFRP Bars
Publication: Journal of Composites for Construction
Volume 28, Issue 4
Abstract
The combination of glass fiber–reinforced polymer (GFRP) and ultrahigh-performance concrete (UHPC) to form structural members has generated significant interest due to their excellent durability and mechanical properties. This paper presents the flexural behavior and design methodology of GFRP-reinforced UHPC beams. Eight reinforced UHPC beams were tested to failure, varying in longitudinal reinforcement type (steel and GFRP), flexural reinforcement ratio, and steel fiber volume fraction (1% and 2%). Two flexural failure modes, including crack localization followed by rupture of GFRP (tension failure) and progressive crushing of UHPC followed by rupture of GFRP (compression failure), were observed in the tested GFRP-reinforced beams. Substitution of steel bars with GFRP bars resulted in delayed crack localization and a significant improvement in flexural strength by 54.9% and ultimate displacement by 55.7%. Increasing the GFRP reinforcement ratio showed a trend of increased flexural capacity, ultimate deformation, and energy dissipation capacity. Increasing the steel fiber volume in UHPC improved the flexural capacity of the tension failure–controlled beam, but had a slight effect on the flexural capacity of the compression failure–controlled beam. In addition, two different models were used to calculate beam deflection, and were compared with experimental results at the service load levels. Considering the fiber-bridging mechanism, a flexural strength model for GFRP-reinforced UHPC beams was developed. Finally, a minimum reinforcement ratio was proposed to ensure progressive failure of GFRP-reinforced UHPC beams.
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Data Availability Statement
All data, models, and codes generated or used during the study appear in the published article.
Acknowledgments
The authors gratefully acknowledge the financial support provided by the National Natural Science Foundation of China (Nos. 52008165 and 52130806) and the Program Fund of Non-Metallic Excellence and Innovation Center for Building Materials (2023TDA4-1).
Notation
The following symbols are used in this paper:
- Af
- area of tensile FRP reinforcements;
- a
- shear span;
- b
- beam width;
- cb
- depth of the neutral axis;
- c0
- depth between the neutral axis and the position where is located;
- d
- effective depth;
- Ec
- elastic modulus of UHPC;
- Eel
- elastic energy;
- Etot
- total energy;
- fcr
- cracking tensile strength of UHPC;
- fcu
- compressive strength of UHPC;
- ff
- tensile stress in FRP;
- ffu
- ultimate tensile strength of FRP;
- ftu
- ultimate tensile strength of UHPC;
- h
- depth of the beam section;
- Icr
- transformed moment of inertia of the cracked section;
- Ig
- gross moment of inertia of uncracked section;
- Ie
- effective moment of inertia;
- L
- clear span;
- lf
- length of steel fiber;
- Ma
- applied bending moment;
- Mcr
- cracking moment;
- Mcr,pred
- predicted cracking moment;
- Mn
- maximum moment;
- Mn,pred
- predicted maximum moment;
- Mu
- ultimate moment;
- P
- applied load;
- Vf
- steel fiber volume fraction;
- yt
- distance from neutral axis to extreme tension fiber;
- σ
- stress in UHPC;
- ɛ
- strain in UHPC;
- UHPC strain at the extreme compression fiber of the section;
- ultimate compressive strain of UHPC;
- UHPC compressive strain at which the compressive strength is reached;
- tensile strain in FRP;
- ultimate tensile strain of FRP;
- ɛt,cr
- cracking tensile strain of UHPC;
- ɛt,loc
- localization strain of UHPC;
- ɛt,lim
- UHPC tensile strain at which the tensile stress is reduced to zero;
- Δ
- midspan deflection;
- Δcr
- cracking deflection;
- Δpeak
- deflection corresponding to the maximum capacity;
- Δs
- service deflection;
- Δs,pred
- predicted service deflection;
- Δu
- ultimate deflection;
- μe
- energy-based ductility index;
- ζ
- plastic influence coefficient;
- ρ
- flexural reinforcement ratio;
- ρb
- balanced reinforcement ratio;
- ρmin
- minimum FRP reinforcement ratio required to ensure progressive failure; and
- γ
- factor that depends on the boundary conditions and the type of applied load.
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History
Received: May 24, 2023
Accepted: Feb 20, 2024
Published online: Apr 23, 2024
Published in print: Aug 1, 2024
Discussion open until: Sep 23, 2024
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