Improving the Load-Carrying Capacity of FRP-to-Concrete Bonded Joints Using a Biaxial GFRP Interlayer
Publication: Journal of Composites for Construction
Volume 28, Issue 4
Abstract
The use of externally bonded (EB) fiber-reinforced polymer (FRP) systems for the strengthening of reinforced concrete (RC) structures is a widely accepted technique. In these strengthened systems, debonding of the FRP laminate from the concrete substrate is a commonly observed failure mode, which controls the strength of the bonded joint. Debonding failure often limits the utilization of the strength of carbon fiber–reinforced polymer (CFRP) laminates, which reduces the efficiency of the strengthening system. This paper presents a novel methodology to improve the load-carrying capacity (i.e., ultimate load) of CFRP-to-concrete bonded joints, therefore improving the utilization of the CFRP material strength. A bidirectional glass fiber–reinforced polymer (GFRP) interlayer is introduced between the CFRP laminate and the concrete substrate, therefore, distributing the load that is applied to the CFRP laminate over a larger bond area than that of typical CFRP-to-concrete bonded joints. A series of single-shear pull test specimens were fabricated and tested to investigate the behavior of the newly proposed bonded joints. A vacuum curing technique was employed to achieve a good quality bonded interface. The test results showed a significant increase in the ultimate load. In addition, the test results showed that the GFRP laminate width and stiffness significantly affect ultimate load (up to 156% increase). Considering the significantly lower cost of GFRP compared with CFRP laminates, the proposed method could provide an economical solution to improve the efficiency of EB CFRP strengthening systems.
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Data Availability Statement
All data, models, and codes generated or used during the study appear in the published article.
Notation
The following symbols are used in this paper:
- bp
- width of CFRP laminate;
- Ep
- elastic modulus of the CFRP laminate;
- Gf
- interfacial fracture energy per unit area of the bonded joint;
- KInii
- initial stiffness (kN/mm);
- Li
- distance to ith data point measured from the free end of the CFRP laminate;
- n
- number of data points measured from the free end of the CFRP laminate to the current collecting point;
- Pu-
- ultimate load (kN);
- Pu-ref
- ultimate load of the reference specimens (kN);
- tp
- thickness of the CFRP laminate;
- δi/2
- slip at the middle point between the ith and (i + 1)th data point;
- strain value collected from the DIC analysis at the ith data point measured from the free end of the CFRP laminate;
- σc
- normal stress that acts on concrete;
- σgp
- normal stress that acts on the bonded interface;
- σp
- normal stress that acts on CFRP laminate;
- τi/2
- shear stress at the middle point between the ith and (i + 1)th data point; and
- τ
- interfacial shear stress.
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Information & Authors
Information
Published In
Journal of Composites for Construction
Volume 28 • Issue 4 • August 2024
Copyright
© 2024 American Society of Civil Engineers.
History
Received: May 14, 2023
Accepted: Jan 5, 2024
Published online: May 24, 2024
Published in print: Aug 1, 2024
Discussion open until: Oct 24, 2024
ASCE Technical Topics:
- Bonding
- Carbon fibers
- Composite materials
- Engineering materials (by type)
- Fiber reinforced composites
- Fiber reinforced polymer
- Fibers
- Joints
- Laminated materials
- Material mechanics
- Material properties
- Materials engineering
- Materials processing
- Polymer
- Strength of materials
- Structural engineering
- Structural members
- Structural systems
- Synthetic materials
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