Externally Bonded CFRP for Flexural Strengthening of RC Beams with Different Levels of Soffit Curvature
Publication: Journal of Composites for Construction
Volume 26, Issue 1
Abstract
This paper reports a comprehensive study on the behavior of concavely curved soffit reinforced concrete (RC) beams strengthened in flexure with carbon fiber-reinforced polymer (CFRP) composites under static loading. The main objective of this paper is to explore the effect of surface concavity on the bond performance of externally bonded wet layup CFRP sheets and laminates. An experimental program consisting of flexural strengthening of 24 RC beams with concavely curved soffits was carried out. All specimens were simply supported RC beams tested under three-point bending. Of the 24 beams, 6 beams were flat soffit RC beams, and the remainder were fabricated with concavely curved soffits with a degree of curvature that is ranging from 5 mm/m to 20 mm/m. All tested specimens were 2,700-mm long and had a constant cross section at midspan of 140-mm wide × 260-mm deep. The experiments showed that all strengthened beams failed by intermediate crack-induced (IC) debonding of the CFRP. The experimental results were then used, together with those for other specimens in the literature to set recommendations for strengthening concavely curved RC beams.
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Acknowledgments
The joint scholarship support provided to the first author by the Iraqi Ministry of Higher Education and Scientific Research and the Swinburne University of Technology is gratefully acknowledged. The authors wish to acknowledge the technical support provided by the staff of the Smart Structures Laboratory of the Swinburne University of Technology.
The support of BASF (Australia) is gratefully acknowledged for supplying all the FRP and epoxy material used.
Notation
The following symbols are used in this paper:
- section depth at midspan, mm;
- ɛfd
- debonding strain of externally bonded FRP reinforcement;
- n
- number of plies of FRP reinforcement;
- Ef
- static modulus of elasticity of FRP, MPa;
- tf
- thickness of FRP reinforcement;
- ɛfk
- characteristic ultimate strain of FRP;
- γFRP,mɛ
- design partial safety factor for FRP strain;
- Vu
- nominal shear strength of the section including concrete and steel ligatures calculated as per AS 5100.5 (AS 2017a);
- Vc
- nominal shear strength provided by the concrete with steel flexural reinforcement calculated as per ACI 318M-19 (ACI 2019);
- VRd
- shear strength of concrete section including shear reinforcement calculated as per BS EN 1992-1-1;
- τlong
- longitudinal shear stress between the FRP and the concrete near the ends of the FRP;
- τlim,c
- longitudinal shear stress between the FRP and the concrete near the ends of the FRP;
- characteristic compressive strength of concrete as per AS 5100.5 (AS 2017a);
- fctk
- characteristic concrete tensile strength as per BS EN 1992-1-1; and
- γc
- partial safety factor of concrete to be taken as 1.5 as per BS EN 1992-1-1.
References
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Published In
Journal of Composites for Construction
Volume 26 • Issue 1 • February 2022
Copyright
© 2021 American Society of Civil Engineers.
History
Received: May 9, 2021
Accepted: Sep 20, 2021
Published online: Nov 12, 2021
Published in print: Feb 1, 2022
Discussion open until: Apr 12, 2022
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