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Reinforced Concrete Beams Analyzed with Rayleigh Fibre Optic Strain Sensing

A vast amount of North America’s reinforced concrete infrastructure is deteriorating and reaching the end if its design life. One potential way to extend the service life of these structures is to use structural health monitoring (SHM) technologies to better assess the effects of deterioration. Fibre optic sensors (FOS) using rayleigh optical backscatter reflectometry offer the unique capability to measure strain along the whole fibre over small gauge lengths potentially with microstrain resolution. These systems could be used to provide critical insight into deterioration mechanisms. However, before these systems can be used in SHM applications, installation techniques need to be developed and measurement accuracy confirmed. In this study, reinforced concrete beams instrumented with both conventional strain gauges and FOS were tested. A number of fibre optic installation methods were evaluated (e.g. internally tied and bonded fibres and externally epoxied fibres) to determine which provided the most accurate results. The accuracy of the FOS measurements was found to be a function of the type of bonding used although excellent correlation with strain gauge results was found in some cases. Further work is required to determine whether the FOS can be used to accurately locate and quantify localized steel deterioration in reinforced concrete structures.

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