Fiber optic sensors in concrete structures: a review

Fiber optic sensors (FOSs) are ideally suited for monitoring strain in concrete structures due to their small size, low cost, ability to be embedded internally, and multiplexing capabilities. Several types of fiber optic strain sensor have been developed, including those based on intensity, polarization, interferometry, and fiber Bragg gratings (FBGs). The FBGs have the advantage of being absolute, linear in response, interrupt immune, and most readily multiplexed. The ability of embedded and surface mounted FOSs to detect strain in reinforced concrete has been demonstrated in several laboratory tests. Comparisons between various FOSs and traditional foil strain gages show good agreement. Sensors have been surface mounted on existing bridges to evaluate observed cracking and to monitor vibration due to traffic loading. FOSs have also been embedded in several newly constructed civil structures, including bridges, buildings, and dams, yielding information about static and dynamic strain, temperature, wind or water pressure, and structural health. Practical and logistical challenges to routine implementation of FOSs in civil structures are being addressed with each additional application.