Highly Dense Strain Measurement Of Concrete Retrofitted With Smart Fabric

A significant technical advancement in distributed fiber optic strain sensors has been accomplished: Brillouin optical correlation domain analysis (BOCDA) provides a high spatial resolution and the smallest measurement interval due to Brillouin scattering stimulated by the correlation of two counter-propagating lightwaves. In a BOCDA-based system, the measurement position can be varied continuously by changing the modulation frequency, whereas other systems require a sophisticated A/D board for localizing the measurement position. In fact, 50 mm is the current limit of the measurement interval in conventional time-domain-based systems, because higher sampling rates are required to process information traveling at the speed of lightwaves. This paper presents an experimental study on cracked concrete specimen retrofitted with a ply of smart fabric; a fiber optic sensor (FOS) is woven into the fabric. The strain distribution along the sensing fiber is measured to detect the debonding of the smart fabric from the concrete specimen under loading, and the measured highly dense strain information obtained using BOCDA is found to potentially facilitate a better understanding of structural behavior.