| 1. |
- Rempling, Rasmus, 1976, et al.
(författare)
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The need for research and innovation to facilitate upscaling of low-carbon concrete
- 2023
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Ingår i: IABSE Congress New Delhi 2023 Engineering for Sustainable Development. - : International Association for Bridge and Structural Engineering (IABSE). - 9781713883128 ; , s. 1199-1206
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Konferensbidrag (refereegranskat)abstract
- For decades, research has been carried out with a focus on concrete structures during curing to mitigate the risk of thermal cracking. Computer programs and aids/tools have also been developed to assess stress and cracking risk analysis of concrete structures during curing. However, today with the recent introduction of low-carbon concretes to reduce the environmental impact of constructions, the reliability of the tools and working procedures, i.e. concrete characterization, is questioned, and a roadmap for research and innovation is called for. The project's primary purpose is to investigate the need for research and innovation regarding upscaling the usage of low-carbon concrete. The nature of the study is based on an industry-focused workshop with specialists from Scandinavia. Increased knowledge of hardening concrete's cracking risk-related properties is of the utmost importance for the construction industry as the need for its understanding has recently increased.
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| 2. |
- Chen, Teresa E, 1988, et al.
(författare)
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Comparison of the service life, life-cycle costs and assessment of hybrid and traditional reinforced concrete through a case study of bridge edge beams in Sweden
- 2023
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Ingår i: Structure and Infrastructure Engineering. - : Informa UK Limited. - 1573-2479 .- 1744-8980. ; 19:1, s. 39-57
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Tidskriftsartikel (refereegranskat)abstract
- The edge beams of reinforced concrete bridges with de-icing salts sprayed experience extensive corrosion damage. The average service life of edge beams needing replacement in Sweden has been reported as only 45 years, causing great economic loss to both owners and users. Hence, finding a durable solution for edge beams would benefit society. Hybrid reinforced concrete structures, produced by adding a low-to-moderate fibre content into traditional reinforced concrete, can effectively limit the service crack width and improve resistance to chloride-induced corrosion damage. In this paper, different alternatives of hybrid and traditional reinforced edge beams were designed for a case study. The service life of the alternatives was compared by conducting chloride diffusion calculations and by applying a corrosion-induced cracking model. The economic and environmental (indicated by greenhouse gas emissions) benefits of using hybrid reinforced edge beams were assessed by life-cycle cost analysis and life-cycle assessment. The results showed that the service life of edge beams made of hybrid reinforced concrete can be prolonged by over 58%, thereby enabling a significant reduction in the total life-cycle costs and annual total greenhouse gas emissions.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Fernandez, Ignasi, 1984, et al.
(författare)
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Two-dimensional strain field analysis of reinforced concrete D-regions based on distributed optical fibre sensors
- 2023
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Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 278
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Tidskriftsartikel (refereegranskat)abstract
- The introduction of Distributed Optical Fibre Sensing in experimental testing of reinforced concrete structures has enabled the acquisition of measurements with an unparalleled level of detail, providing an accurate and ubiquitous description of cracking and deflections throughout an element. However, most of the available research using this technology has focused on the study of beam specimens and high quality data for the calibration and development of models that can describe accurately the behaviour of D-regions in service is still lacking. For that reason, the application of distributed optical fibre sensing in D-regions remains a subject of interest. In this work a method for the deployment of fibre sensors in a multilayer configuration is presented for a wall element. An interpolation approach is then proposed, which combined with the distributed nature of the sensors enabled the description of detailed heat maps for the global and principal strain fields. The results indicated that shear strains can reveal the position of shear cracks well before they are formed whereas the maximum and minimum principal strains clearly show the crack pattern and crack development as well as the load transfer mechanisms including, for the first time, the experimental identification of a secondary strut-and-tie mechanisms.
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| 7. |
- Gil Berrocal, Carlos, 1986, et al.
(författare)
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Analysis of the flexural response of hybrid reinforced concrete beams with localized reinforcement corrosion
- 2023
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Ingår i: Structural Concrete. - 1751-7648 .- 1464-4177. ; 24:4, s. 4799-4822
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a modeling approach to analyze the flexural response of hybrid reinforced concrete beams with localized corrosion. A new mechanical model based on extensive uniaxial testing is proposed to describe the stress–strain relationship of corroded bars with a single pit. The proposed mechanical model is then incorporated into a sectional analysis to determine the moment curvature relationship of hybrid reinforced concrete sections with pitting corrosion. The actual crack pattern is used to divide a beam into discrete hinge elements which are then combined to compute the load–deflection response of statically determinate beams. The modeling approach is evaluated with available experimental data showing good predictive capabilities. A parametric study revealed the importance of the interaction between the tensile reinforcement ratio and the concrete postcracking residual stress. Furthermore, the deformation capacity of reinforcement bars with pitting corrosion levels beyond 0.25 was shown to have a dominant effect on the ultimate deflection of hybrid reinforced concrete beams.
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| 8. |
- Gil Berrocal, Carlos, 1986, et al.
(författare)
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Strain and Temperature Monitoring in Early-Age Concrete by Distributed Optical Fiber Sensing
- 2023
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Ingår i: Proceedings SynerCrete 2023 International RILEM Conference on Synergising Expertise towards Sustainability and Robustness of Cement-based Materials and Concrete Structures. - : Springer Nature. ; , s. 913-924, s. 913-924
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the way towards a carbon neutral construction industry, the partial substitution of cement clinker by alternative binders is becoming increasingly popular in the design of low-carbon concrete mixes. However, as new concrete mixes are developed, the parameters governing the risk of early-age cracking arising from restraint forces due to thermal and shrinkage deformations need to be investigated for each mix. This paper reports the results of a field test in which distributed optical fiber sensors (DOFS) were used to monitor strain and temperature in two large-scale prisms cast against the ground. One of the specimens was cast with a reference concrete mix with CEM I whereas in the other mix cement was partly replaced by fly ash. After casting, mineral wool was used to insulate the specimens in order to reproduce realistic conditions in large mass concrete elements. Temperature measurements enabled a direct comparison of the heat generated by each mix as well as the estimation of the strength development. Strain measurements, on the other hand, gave an indication of the variation of the degree of restraint along the height of the specimens. Using available models for concrete creep, the tensile stresses along the specimens were calculated at different heights and compared to the expected tensile strength in order to assess the crack risk. After removing the insulation, measured strains exhibited a strong dependence on external temperature variations. The test results proved useful to analyse the early-age behaviour of concrete.
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| 9. |
- Jansson, August, 1994, et al.
(författare)
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Investigation of the Impact of Concrete Surface Treatment Methods on the Interfacial Bond Strength
- 2023
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Ingår i: RILEM Bookseries. - 2211-0844 .- 2211-0852. ; , s. 925-934
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Konferensbidrag (refereegranskat)abstract
- Fibre-reinforced shotcrete (FRS) tunnel linings in hard rock are structurally intricate due to the complexity of rock mechanics and the interaction between shotcrete and rock. As the consequences of tunnel failure can be severe, maintaining the structural safety is vital in an operating tunnel. However, to satisfy safety demands, design- and maintenance measures can be conservative, as empirical methods and worst-case scenarios are commonly used in design and repair to account for the complexity of the system. A novel method for verification of tunnel linings, combining experiments, state-of-the-art distributed optical fibre sensing systems embedded in the shotcrete, advanced finite element modelling, and machine learning algorithms is in development. For the experiments, the characterisation of bond strength between rock and FRS are crucial to simulate trustworthy data. In this paper, a literature review and experiments are presented aiming to characterise a high and a low, non-zero, interfacial bond strength between two layers of concrete. The properties of the substrate surface in terms of roughness, microcracks, cleanliness and free water are investigated before casting. The experiments study four different surface treatments, including jackhammering, grinding, grinding and adding a layer of sand to the surface, and grinding and adding free water to the surface. The literature review showed hydrodemolition as a surface treatment method to have a consistently high bond strength, while the experiments showed a lower bond strength for ground surfaces than for jackhammered specimens. The inclusion of sand did not significantly decrease the bond strength, while the addition of water slightly increased the strength.
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