| 1. |
- Bado, Mattia Francesco, et al.
(författare)
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Characterization of concrete shrinkage induced strains in internally-restrained RC structures by distributed optical fiber sensing
- 2021
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Ingår i: Cement and Concrete Composites. - : Elsevier BV. - 0958-9465. ; 120
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Tidskriftsartikel (refereegranskat)abstract
- The present paper reports the result of an inter-university experimental investigation on concrete shrinkage induced strains on embedded rebars instrumented with Distributed Optical Fiber Sensors (DOFS). The monitoring was performed for a standard 28 days drying time and for a shorter 6 days time span (reflecting realistic constructions schedules accelerations to meet set deadlines). The tested specimens were Reinforced Concrete (RC) tensile members differing in their geometry, DOFS employed and fiber/rebar bonding techniques. Regarding the latter, a combination of cyanoacrylate (for gluing) and silicone (protection) was found to be the optimal one for deployments inside RC structures. The DOFS-reported combined effect of concrete shrinkage and creep on the embedded rebars is compared with the Model Code 2010's predictions and employed to extract conclusions on the residual performance of the RC members at the end of their drying phase.
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| 2. |
- Bado, Mattia Francesco, et al.
(författare)
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Distributed optical fiber sensing bonding techniques performance for embedment inside reinforced concrete structures
- 2020
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 20:20, s. 1-23
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Tidskriftsartikel (refereegranskat)abstract
- Distributed optical fiber sensors (DOFS) are modern-day cutting-edge monitoring tools that are quickly acquiring relevance in structural health monitoring engineering. Their most ambitious use is embedded inside plain or reinforced concrete (RC) structures with the scope of comprehending their inner-workings and the functioning of the concrete-reinforcement interaction. Yet, multiple studies have shown that the bonding technique with which the DOFS are bonded to the reinforcement bars has a significant role on the quality of the extracted strain data. Whilst this influence has been studied for externally bonded DOFS, it has not been done for embedded ones. The present article is set on performing such study by monitoring the strain measurement quality as sampled by DOFS bonded to multiple rebars with different techniques and adhesives. These instrumented rebars are used to produce differently sized RC ties later tested in tension. The discussion of the test outputs highlights the quasi-optimal performance of a DOFS/rebar bonding technique consisting of incising a groove in the rebar, positioning the DOFS inside it, bonding it with cyanoacrylate and later adding a protective layer of silicone. The resulting data is mostly noisefree and anomalies-free, yet still presents a newly diagnosed hitch that needs addressing in future research.
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| 3. |
- Gil Berrocal, Carlos, 1986, et al.
(författare)
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Assessment and visualization of performance indicators of reinforced concrete beams by distributed optical fibre sensing
- 2021
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Ingår i: Structural Health Monitoring. - : SAGE Publications. - 1475-9217 .- 1741-3168. ; 20:6, s. 3309-3326
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Tidskriftsartikel (refereegranskat)abstract
- The implementation of structural health monitoring systems in civil engineering structures already in the construction phase could contribute to safer and more resilient infrastructure. Due to their lightweight, small size and high resistance to the environment, distributed optical fibre sensors stand out as a very promising technology for damage detection and quantification in reinforced concrete structures. In this article, the suitability of embedding robust distributed optical fibre sensors featuring a protective sheath to accurately assess the performance indicators, in terms of vertical deflection and crack width, of three reinforced concrete beams subjected to four-point bending is investigated. The results revealed that a certain strain attenuation occurs in embedded robust distributed optical fibre sensors compared to commonly used thin polyimide-coated distributed optical fibre sensors bonded to steel reinforcement bars. However, the presence of the protective sheath prevented the appearance of strain reading anomalies which has been a frequently reported issue. Performance wise, the robust distributed optical fibre sensors were able to provide a good estimate of the beam deflections with errors of between 12.3% and 6.5%. Similarly, crack widths computed based on distributed optical fibre sensor strain measurements differed by as little as ±20 µm with results from digital image correlation, provided individual cracks could be successfully detected in the strain profiles. Finally, a post-processing procedure is presented to generate intuitive contour plots that can help delivering critical information about the element’s structural condition in a clear and straightforward manner.
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