Abstract
Abstract. Distributed fiber optic strain measurement based on Rayleigh scattering has recently become increasingly popular in automotive and mechanical engineering for strain monitoring and in the construction industry, especially structural health monitoring. This technology enables the monitoring of strain along the entire fiber length. This article addresses integrating optical fibers of different coatings into the concrete matrix to measure the shrinkage deformations. However, previous studies do not give a clear statement about the strain transfer losses of fiber optic sensors in this application. In this context, three different coating types were investigated regarding their strain transfer. The fibers were integrated into fine-grained concrete prisms, and the shrinkage strain was compared with a precise dial gauge. The analysis shows a high correlation between the reference method and the fiber measurement, especially with the ORMOCER® coating. The acrylate coating used is also consistent in the middle area of the specimen but requires a certain strain introduction length to indicate the actual strain. The main result of this study is a recommendation for fiber coatings for shrinkage measurement in fine-grain concretes using the distributed fiber optic strain measurement. In addition, the advantages and disadvantages of the measurement method are presented.
Highlights
The development of fiber optic sensors (FOSs), primarily distributed measurement methods, has led to exciting application scenarios in recent years (Udd, 2011; Parker et al, 1997; Czarske and Müller, 1994; Horiguchi et al, 1995)
The test design is well suited for assessing the shrinkage behavior with fiber optic strain measurements
The results indicate that the ORMOCER® coating material can be used for adequate strain measurement in fine-grain concretes
Summary
The development of fiber optic sensors (FOSs), primarily distributed measurement methods, has led to exciting application scenarios in recent years (Udd, 2011; Parker et al, 1997; Czarske and Müller, 1994; Horiguchi et al, 1995). Measurement methods based on Rayleigh, Brillouin, and Raman scatterings are suitable for the measurement tasks in SHM because of their distributed measurement principle. While Raman scattering only measures temperatures, Brillouin and Rayleigh scatterings can measure the temperature and strain (López-Higuera et al, 2011). The difference between these two methods can be found in the spatial resolution, maximum measuring length, and accuracy. Using Brillouin scattering, measurement tasks of several kilometers can be realized with a spatial resolution in the centimeter range (Parker et al, 1997; Leung et al, 2013; Song et al, 2010). Rayleigh scattering used in this study has a maximum measuring length of approximately 70 m and a spatial resolution of a few millimeters (Samiec, 2012)
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