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Engineering

Research project: Bond improvement methods for FRP internal reinforcement in concrete beams

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The high-strength, light-weight and non-corrosive properties of Fibre Reinforced Polymers (FRP) make them attractive as a reinforcement material in concrete. Despite the growing popularity of FRPs as a means of repairing/strengthening concrete structures, FRP rupture and premature debonding have inhibited the industry-wide acceptance of FRP internal reinforcement systems in concrete. Our research demonstrates the potential use of FRP laminates as a viable internal reinforcing material for reinforced concrete. However, a detailed investigation onto the concrete–FRP bond is required in order to achieve desirable strengths and ductility in concrete structures.

Project Overview

FRP systems
Fig 1
diagram
Fig 2

Fig. 1 Externally-bonded FRP systems on concrete often fail in premature debonding

Fig. 2 Anchorage systems able to delay the debonding of externally-bonded FRPs on concrete

Bond improvement for FRP internal reinforcement

Although the provision of anchorage systems that prevent premature debonding of externally-bonded FRPs on concrete is straightforward, the methods are impossible to use for internal FRP systems. We investigated the effectiveness of several new techniques of improving the bond between the internal FRP reinforcement and in situ concrete.

 

 

FRP
Fig 3

Fig. 3 Bond improvement methods for FRP internal reinforcement in concrete: (a) Wet-epoxy resin on plain FRP surfaces, (b) Aggregate coating, (c) Lipped-channel with intermittent closed loops, and (d) Aggregate coating on a lipped channel section with intermittent closed loops

 

FRP reinforcements for strong and ductile concrete beams

We developed a combined flexural and shear internal reinforcement system made from carbon fibre reinforced polymer (CFRP) fabric. This system ensured improved bond performance between the reinforcement and in situ concrete. For example, applied load–midspan deflection relationship shown in Fig. 4 demonstrates the better composite action (higher strength and ductility before final failure) between the FRP reinforcement and the concrete in a beam.

graph
Fig 4

Fig. 4 Load-midspan deflection relationship of a concrete beam reinforced with a combined flexural and shear FRP reinforcement

 

Benefits to structural engineering

The results of this project would provide knowledge and confidence to use efficient concrete structural forms; the consequent changes the designers would make will help to reduce the carbon footprint.

The work could also lead to new multi-disciplinary research in the fields of architectural and structural engineering.

The construction industry may be able to explore the application of new concrete structures in marine/offshore and other critical environments where the conventional reinforced concrete structures require frequent monitoring and maintenance.

 

Research collaborator

Dr Alan Bloodworth, University of Warwick

 

Funding sources

The Institution of Civil Engineers

 

Relevant publications

Achintha, M, Alami, F, Harry, S and Bloodworth, A (2016) Towards Innovative FRP Fabric Reinforcement in Concrete Beams: Concrete–CFRP Bond. Magazine of Concrete Research (Under review).

Achintha, M, Alami, F, and Bloodworth, A (2015) An CFRP fabrics as internal reinforcement in concrete beams’. 7th Int. Conf. on Advanced Composites in Construction, Cambridge, UK, 9-11 September.

 

Further information

Please contact Dr Mithila Achintha (E-mail: Mithila.Achintha@soton.ac.uk or 02380 59 2924)

 

 

Related research groups

Engineering Materials
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