Shear crack width assessment in concrete structures by 2D distributed optical fiber

Abstract

This paper outlines the second part of an experimental study to show the capabilities of distributed optical fiber sensors (DOFS) in their application to the structural health monitoring (SHM) of the shear performance of concrete structures. SHM seeks to obtain the shear crack characteristics of concrete elements: detection, localization and quantification of shear damage. The two first were discussed in the first part of the experimental study. In the present paper, the quantification is dealt with by proposing a method to obtain the mean shear crack width in concrete beams. The method is based on the experimental data obtained by a DOFS bonded to the concrete surface. First, the basis of the methodology are presented and, later on, experimentally checked by testing of three partially pre-stressed concrete (PPC) beams subjected to a shear test with increasing level of load. The DOFS were deployed in the web of the beams to conform a 2D grid mesh to measure the strain profile along two orthogonal directions. The experimental data was obtained using an OBR (Optical Backscattered Reflectometer) system with high spatial resolution and sensitivity that allow a complete mapping of the cracking pattern and to obtain the required data for the calculation of the crack width. The results show the feasibility of the proposed method in calculating the shear crack width when compared to the results from traditional instrumentation.

Crack monitoring in reinforced concrete beams by distributed optical fiber sensors

“…Their method was evaluated experimentally using crack measurements obtained by magnetic transducers from a RC slab tested in bending up to failure and further validated with nonlinear finite element modelling. A similar approach was used in (Rodriguez, Casas, & Villalba, 2019) to quantify the width of shear cracks, where the authors bonded DOFS on the surface of the web of three concrete beams to create a two-dimensional grid of fiber sensors able to measure strain profiles in two orthogonal directions. In both studies the crack width estimations obtained by their method based on the strain profiles measured by the DOFS compared well with the crack width measurements from transducers.…”

A Review of Recent Distributed Optical Fiber Sensors Applications for Civil Engineering Structural Health Monitoring

“…was compared with the more traditional one based on the deployment of displacement rosettes in [65]. The results showed a relative similarity between the two analyses' results despite some mismatches attributed to the high level of measurement error involved in the rosette method.…”

“…Shear failure was also analyzed in Rodriguez et al [ 64 , 65 ] who investigated an experimental methodology to obtain the shear cracking pattern of RC beams. In particular, the latter suggested the formation of a 2D grid composed of one or two OFDR DOFS bonded to the shear span of a beam.…”

“…Apart from the definition of the crack pattern, an algorithm was also proposed to calculate the crack widths based on the strain profiles in both horizontal and vertical directions. On the extraction of the above shear crack widths, the proposed DOFS method was compared with the more traditional one based on the deployment of displacement rosettes in [ 65 ]. The results showed a relative similarity between the two analyses’ results despite some mismatches attributed to the high level of measurement error involved in the rosette method.…”

Dehnungsmessung bei mehraxialen Druckversuchen an Beton mittels faseroptischer Sensoren

“…Basierend auf dem Coating (Bild 1) variieren die für verlustfreie Weiterleitung des Lichts möglichen Umlenkradien und auch die Steifigkeiten der Fasern [18, 27, 30]. Im Stahlbetonbau eignen sich diese „blanken“ Fasern vor allem für die Applikation auf erhärteten Probekörperoberflächen [31–36] oder entlang von Bewehrungsstäben bzw. innerhalb von in die Stäbe gefrästen oder geätzten Nuten [29, 30, 35, 37–40].…”