| 1. |
- Fernandez, Ignasi, 1984, et al.
(författare)
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Monitoring of new and existing stainless-steel reinforced concrete structures by clad distributed optical fibre sensing
- 2023
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Ingår i: Structural Health Monitoring. - : SAGE Publications. - 1475-9217 .- 1741-3168. ; 22:1, s. 257-275
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Tidskriftsartikel (refereegranskat)abstract
- The implementation of structural health monitoring systems in existing civil engineering structures could contribute to a safer and more resilient infrastructure as well as important savings. Due to their light weight, small size, and high resistance to the environment, distributed optical fibre sensors (DOFS) stand out as a very promising technology for damage detection and quantification in reinforced concrete structures. This dataset includes information of DOFS featuring an external polymeric cladding with rough surface, deployed in a stainless-steel reinforced concrete beam subjected to four-point bending. Several sensor positions, both embedded in the concrete and attached to the surface, are included in a multilayer configuration. The data of the sensors includes two series of test, first cyclic loading under service loads and lastly cyclic loading to failure. Additionally, data from Digital Image Correlation and the actuator recordings are included for cross-validation purposes.
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| 2. |
- 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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| 3. |
- Berrocal, Carlos Gil, 1986, et al.
(författare)
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Corrosion-induced cracking and bond behaviour of corroded reinforcement bars in SFRC
- 2017
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Ingår i: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 113, s. 123-137
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates, experimentally and numerically, the effect of fibre reinforcement on the initiation of corrosion-induced cracks in concrete and the bond behaviour of corroded reinforcement bars in fibre reinforced concrete. The fibres, due to their confining effect, contributed to delay crack initiation, improve the post-peak bond behaviour and retain the initial splitting strength for corrosion levels of up to 8%. The mechanisms for delayed crack initiation were explained through 3D finite element analyses of the experiments whereas a 1D model, using experimental bond-slip curves as an input, was employed to quantify the beneficial effect of fibres on the reinforcement anchorage length.
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| 4. |
- Berrocal, Carlos Gil, 1986, et al.
(författare)
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Corrosion-induced cracking and bond behaviour of corroding reinforcement bars in SFRC
- 2017
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Ingår i: Nordic Concrete Research. - 0800-6377. - 9788282080569 ; , s. 123-126
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Konferensbidrag (refereegranskat)abstract
- In this study, an experimental programme has been carried out to investigate the influence of fibres on the onset of corrosion-induced splitting cracks. Cylindrical lollipop specimens with a centrally positioned Ø16 mm bar and varying cover depths from 40 to 64 mm were subjected to accelerated corrosion. A constant current of 100 μA/cm2 was impressed through the specimens and the electrical resistance between each rebar and an external copper mesh acting as cathode was monitored. The fibres, due to their confining effect, contributed to delay crack initiation, improve the post-peak bond behaviour and retain the initial splitting strength for corrosion levels of up to 8%.
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| 5. |
- Berrocal, Carlos Gil, 1986, et al.
(författare)
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Influence of fibre reinforcement on the initiation of corrosion-induced cracks
- 2016
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Ingår i: Materials, Systems and Structures in Civil Engineering 2016 - Segment on Service Life. - 9782351581704 ; 1, s. 231-240
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Konferensbidrag (refereegranskat)abstract
- The initiation of corrosion-induced cracks, often running parallel to the reinforcement, becomes a turning point in the service life of a reinforced concrete (RC) structure as they promote increased corrosion rates, thus accelerating the degradation process of the structure. Compared to plain concrete, fibre reinforced concrete (FRC) provides additional confinement to the reinforcement, which has been reported to delay or even prevent the appearance of mechanically induced splitting cracks. In this study, an experimental programme has been carried out to investigate the influence of fibres on the onset of corrosion-induced splitting cracks. Cylindrical lollipop specimens with a centrally positioned Ø16 mm bar and varying cover depths from 40 to 64 mm were subjected to accelerated corrosion. A constant current of 100 µA/cm2 was impressed through the specimens and the electrical resistance between each rebar and an external copper mesh acting as cathode was monitored. Crack initiation, determined from a drop in electrical resistance, and confirmed by visual inspection, revealed that fibre reinforcement may delay corrosion-induced cracks, an effect that was more noticeable for reduced c/Ø ratios, featuring up to 50% higher corrosion levels at crack initiation compared to plain concrete.
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| 6. |
- Carro-López, D., et al.
(författare)
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An old bridge transformed into a new one : Possible, recommendable?
- 2019
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Ingår i: 20th Congress of IABSE, New York City 2019. - : International Association for Bridge and Structural Engineering (IABSE). - 9783857481659 ; , s. 951-956
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Konferensbidrag (refereegranskat)abstract
- There is an extensive network of reinforced concrete bridges that give service to roads, highways and railways. These structures where constructed with quality standards of the past, and they suffer of severe problems. Now we consider the idea of substituting them with structural elements with much longer service life. However, there is an important question to be addressed in this area: what to do with the existing infrastructure that would be demolished. Even more if we consider environmental issues. One good example of this recurrent problem could be found in the case of the Gullspång bridge (Sweden). It was constructed in 1935 and it was severely damaged with corrosion. The administration decided in the 2016 that no further repair would be done and that the bridge would be demolished and a new erected in substitution. A fraction of the concrete from the old bridge was crushed and processed to produce new aggregate. With this aggregate, using the coarse fraction, it was analyzed the structural effect of replacing natural aggregates with these recycled aggregates. The performance of the new structural elements was positive, and it seems that a high percentage of the natural aggregates could be replaced with recycled ones.
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| 7. |
- Chen, Teresa E, 1988, et al.
(författare)
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Assessment of the mechanical behaviour of reinforcement bars with localised pitting corrosion by Digital Image Correlation
- 2020
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Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 219
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion of reinforcement in concrete impairs the mechanical behaviour of rebars by decreasing their strength and deformation capacity. In this study, uniaxial tensile tests were carried out on 61 rebars taken from 22 pre- and un- cracked reinforced concrete beams subjected to drying and wetting cycles in chloride solution for over three years. A 3D-scanning technique was used to characterise the maximum local corrosion level, μmax, and different pit shape parameters. Digital Image Correlation (DIC) was used to capture the displacement field of the test bars; the engineering strain was measured through the virtual extensometers created in the DIC post-processing software. The proof and ultimate forces showed linear decreasing trends of μmax, while the proof and ultimate strengths (based on the minimum residual cross-sectional area) were not obviously affected by corrosion. The ultimate strain of corroded bars depended on the gauge length due to strain localisation in the pit. Thus, it was emphasised that the ultimate strain may be overestimated if measured based on a short gauge across the pit. It was also observed that when μmax exceeded a critical local corrosion level (μcrit depending on the ratio between the yield and ultimate strengths of the steel), the region outside the pit did not develop yielding. A lower bound of ultimate strain was further derived as a function of the mechanical parameters of uncorroded steel and maximum local corrosion level. This provided a good comparison with the experimental results. Ultimately, a hypothesis for time-dependent assessment of strain capacity is proposed, considering the evolution of corrosion morphology over time.
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| 8. |
- Dackman, David, 1990, et al.
(författare)
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Correlations Between Localized Pitting Corrosion and Deflection in Reinforced Concrete Beams Subjected to Accelerated Corrosion
- 2023
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Ingår i: RILEM Bookseries. - 2211-0844 .- 2211-0852. ; , s. 902-912
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Corrosion is one of the main deterioration phenomena in reinforced concrete structures. This paper investigates the correlations between localized pitting corrosion and measured performance indicators in reinforced concrete beams subjected to sustained relative deflection and accelerated corrosion through impressed current. Strain measurements from distributed optical fibre sensors were used to calculate the deflection, crack distribution and crack widths over time and thus to quantify changes in performance indicators with corrosion. Once the accelerated corrosion test was concluded, the steel reinforcement bars in the region affected by corrosion were carefully extracted and 3D laser scanning was carried out for the assessment of the reinforcement corrosion. More specifically, laser scanning results were used to identify the localized pitting regions in the vicinity of transversal cracks and consequently the total amount of steel corroded in the same. By assuming the following three hypotheses: (i) an effective pit length at the cracks, (ii) at the beginning of the corrosion process all the applied current and consequently all the corrosion was localized at the pits, (iii) any variation observed in the deflection is attributed to corrosion, therefore proportionality between deflections and loss of steel exists. The total corroded volume of steel was calculated and later compared to the 3D scanning. The results revealed that the volume loss in the pits calculated using Faraday’s law and the proposed method was in very good agreement to the direct volume measured by means of the 3D scanning. Consequently, a direct relation between corrosion and deflection could be established.
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| 9. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Structural performance assessment of post-tensioned concrete beams by embedded continuous fibre optics
- 2023
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Ingår i: IABSE Congress New Delhi 2023 Engineering for Sustainable Development. - 9781713883128 ; , s. 1216-1224
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Konferensbidrag (refereegranskat)abstract
- Prestressed concrete structures have numerous advantages over conventionally reinforced concrete, though the usage of post-tensioned structures has declined over the last two decades. By distributed optical fibre sensors, key performance indicators of the post-tensioned concrete specimens were monitored and evaluated. Initial losses and long-term effects affecting prestressing force, deflections and cracks were tracked and compared to theoretical calculation methods. It was found that the theoretical calculation methods mostly agreed well with results from the distributed optic fibre sensors. The loss of prestressing force due to mechanical creep and relaxation was overestimated in theoretical calculation methods by approximately 6 %, while the loss due to friction was overestimated by 0.6 %. Regarding deflections, the relative error ranged from 0 % to 3.3 % and 0 % to 2.9 % for the reference specimen and post-tensioned beam, respectively.
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| 10. |
- Fahimi, Shayan, et al.
(författare)
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Replication of Crack Pattern in FE Analysis Based on Discretization of Tension Softening Curves
- 2017
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 56:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Today, there is an increasing need for reliable methods for condition assessment and service-life evaluation of existing structures. Although advanced 3D Nonlinear Finite Element (3D NLFE) analysis has proven to be capable of describing the behavior of reinforced concrete in a comprehensive way, the analysis results are difficult to couple with visual inspection data such as cracking and spalling. Moreover, 3D NLFE programs are numerically expensive and incomprehensible for full-scale practical applications. Thus, the present study aims to couple 3D NLFE analysis with condition assessment data, and consequently to increase the accuracy, to optimize the computation time and to improve robustness of such analyses.
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