Abstract

Although some extended studies about the short-term behavior of NSM FRP strengthened beams have been carried out, there is a lack of knowledge about the behavior of this kind of strengthening under sustained loads and high service temperatures. Electromechanical impedance method formulated from measurements obtained from PZT patches gives the ability for monitoring the performance and changes experienced by these strengthened beams at a local level, which is a key aspect considering its possible premature debonding failure modes. This paper presents an experimental testing program aimed at investigating the long-term performance of a concrete beam strengthened with a NSM CFRP laminate. Long term performance under different levels of sustained loading and temperature conditions is correlated with EMI signatures processed using Linear Mixed-effects models. These models are very powerful to process datasets that have a multilevel or hierarchical structure as those yielded by our tests. Results have demonstrated the potential of these techniques as health monitoring methodology under different conditions in an especially complex problem such as NSM-FRP strengthened concrete structures.

Highlights

  • IntroductionStrengthening of reinforced concrete (RC) beams using near surface mounted (NSM)

  • This paper aims to contribute to the study of the behavior of reinforced concrete (RC) beams strengthened with near surface mounted (NSM) fiber-reinforced polymer (FRP) strips under the combined action of sustained loading and temperature variations which, to the knowledge of the author, has not been carried out up to date

  • A remanent strain remained at the midspan of the NSM-FRP laminate after each unloading

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Summary

Introduction

Strengthening of reinforced concrete (RC) beams using near surface mounted (NSM). Fiber-reinforced polymer (FRP) strips and bars has gained greater interest and increased field applications in recent years. In comparison with the more extended methodology of FRP strengthening based on externally bonded reinforcement (EBR), NSM FRP technique presents several advantages such as better anchorage capacity and better protection from accidental damage as those due to, for instance, vandalism and environmental effects [1,2,3]. NSM FRP strengthening does not need much surface preparation except for grooving. The damage needs to be detected in advance or in real time to ensure structural safety and to predict the residual life of FRP composite RC structures in service

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