European Network for Durable Reinforcement and Rehabilitation Solutions

Contract Number: MC-ITN-2013-607851

Bond Behaviour of NSM FRP

Mohamed Reda Emara

Universitat de Girona



Several types of concrete structures are outspread all over the world. During the structures’ service life, several factors can cause deteriorations and decrease its service life. Some of these factors are natural such as accidental loading (earthquakes, wind and blast, etc.) and environmental conditions (temperature, humidity, etc.). Other factors are related to the design process such as changing the structural system or increasing the service load. In order to preserve the exiting concrete structures and increase it service life, strengthening is often needed . Nowadays, FRP materials play an important role in preserving existing concrete structures due to the advantages they provide over other traditional materials.

Use of FRPs in the strengthening of reinforced concrete (RC) structures has been proven to be an efficient technique due to their unique properties. The near-surface mounted (NSM) FRP technique, in which FRP reinforcement is bonded into grooves cut in the concrete cover, has more recently attracted researchers’ attention due to several advantages over the Externally Bonded (EB) FRP systems. The success of a strengthening system is highly dependent on the interfacial bond properties between reinforcement and concrete which depends upon a number of parameters. Although many studies were carried out on the short-term bond behavior of NSM and few others on long-term, still there is a lack and uncertainty about the long-term bond behavior.

In this study, an experimental program is being carried out to investigate the mechanics of bond behavior between NSM FRP reinforcement and concrete when subjected to various environmental conditioning regimes under the effect of immediate and sustained loading. The effect of adhesive type, bond length, temperature, humidity and sustained load level, which are considered to be critical parameters that may affect the bond performance, is being studied. A new test set-up is designed for carrying out the experimental program. Deformations will be measured by means of electrical strain gauges and transducers.

The results of the project will allow expanding the database on bond behavior of NSM FRP strengthening systems, as well as providing guidance for the pull-out testing of NSM FRP systems under sustained loading and combination of temperature and humidity. Furthermore, the results will be used to check validity of existing bond models and propose modifications when needed with the objective of improving the design of NSM FRP strengthened RC elements.


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