SHM by DOFS in civil engineering: a review

Abstract

Abstract. This paper provides an overview of the use of different Distributed Optical Fiber Sensor systems (DOFSs) to perform Structural Health Monitoring (SHM) in the specific case of civil engineering structures. Nowadays, there are several methods available for extracting distributed measurements from optical fiber, and their use have to be according with the aims of the SHM performance. The continuous-in-space data is the common advantage of the different DOFSs over other conventional health monitoring systems and, depending on the particular characteristics of each DOFS, a global and/or local health structural evaluation is possible with different accuracy. Firstly, the fundamentals of different DOFSs and their principal advantages and disadvantages are presented. Then, laboratory and field tests using different DOFSs systems to measure strain in structural elements and civil structures are presented and discussed. Finally, based on the current applications, conclusions and future trends of DOFSs in SHM in civil structures are proposed.

Concrete Crack Monitoring Using a Novel Strain Transfer Model for Distributed Fiber Optics Sensors

“…As the strain varies in concrete structures over important span lengths, the K/λ 2 term is usually lower than 1 µm and therefore can be neglected compared to the crack openings we expect to estimate ( COD 2 >> K λ 2 ). Thus, a symmetrical strain response measured by the optical fiber around the crack location (at z = 0) consists of a crack-induced strain part added to the strain in the host material, whether it is constant: 20) or varies in a linear form:…”

“…With the entire complicated phenomenon, monitoring the crack openings quantitatively using an optical cable bonded along a host material is still a challenge and the idea of measuring strain near cracks is always a complicated problem [19]. Recently, methods of estimating crack openings from distributed strain measurements were presented whether by combination to finite element models [15,20] or through calculation of the optical fiber elongation by summing strain gradients [17,21,22]. However, the limitations of these methods prevailed in the cases of multiple crack propagation and until a certain crack opening limit.…”

Crack monitoring in reinforced concrete beams by distributed optical fiber sensors

“…Raman scattering arises from the thermal vibration of the glass molecules in the fiber core as light travels through the fiber and is highly sensitive to temperature variations (Rodriguez, Casas, & Villalba, 2015b). Brillouin scattering is produced by the interaction of backscattered light and acoustic waves generated when changes in the density of the material occur as a result of thermal effects.…”

“…These inhomogeneities are caused by fluctuations in the density and composition of the fiber core, which makes Rayleigh scattering sensitive to both mechanical strain and temperature changes (Palmieri, 2013). Systems based on Rayleigh scattering are currently limited to a measuring range of up to 2 km, but in exchange they provide an unprecedented spatial resolution that can go down to the the sub-millimetric scale, thereby offering new possibilities for the development of damage detection systems (Rodriguez et al, 2015b).…”

Surface Rust Detection Using Ultrasonic Waves in a Cylindrical Geometry by Finite Element Simulation

“…Example techniques include visual testing [2], modal analysis [3], Eddy current testing [4], thermal infrared testing [5], and ultrasonic testing [6,7]. Among these techniques, fiber optic sensors (FOS) represent a popular approach for long-term monitoring of steel structures [8,9]. While FOS have been applied to many steel structures in the past, most of the damage detection algorithms are based on passive response of FOS.…”