| 1. |
- Williams Portal, Natalie, 1986, et al.
(författare)
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Bending behaviour of novel Textile Reinforced Concrete-foamed concrete (TRC-FC) sandwich elements
- 2017
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Ingår i: Composite Structures. - : Elsevier BV. - 0263-8223 .- 1879-1085. ; 177, s. 104-118
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Tidskriftsartikel (refereegranskat)abstract
- A novel sandwich element design consisting of two facings made of carbon reinforced Textile Reinforced Concrete (TRC), a low density foamed concrete (FC) core and glass fibre reinforced polymer (GFRP) connecting devices was experimentally investigated according to quasi-static and cyclic quasi-static four-point bending. Optical measurements based on Digital Image Correlation (DIC) were taken during testing to enable a detailed analysis of the bending behaviour and level of composite action. A model, verified by the experiments, was developed based on non-linear finite element analysis (NLFEA) to gain further insight on the failure mechanisms. Under both loading conditions, the bending behaviour of the TRC-FC composite elements was characterized by favourable load bearing capacity, partial composite action, superior ductility and multiple fine cracking. The connecting devices were found to be the critical elements causing the initial failure mechanism in the form of localized pull-out within an element.
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| 2. |
- Blomfors, Martin, et al.
(författare)
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Reliability analysis of corroded reinforced concrete beam with regards to anchorage failure
- 2019
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Ingår i: Life-Cycle Analysis and Assessment in Civil Engineering. - : CRC Press/Balkema. - 9781138626331 - 9781351857574 ; , s. 337-344, s. 337-344
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Konferensbidrag (refereegranskat)abstract
- Reinforcement corrosion is a common problem in reinforced concrete infrastructure today, and it is expected to increase in the future. To simply replace the corroded structures with new ones requires large resources, both in financial and environmental terms. Therefore it is important that existing structures are used to their full potential, also after the onset of corrosion. This paper presents a reliability study of the anchorage capacity of a reinforced concrete beam including reinforcement corrosion. The sensitivity of the different input parameters is also studied. As expected, the results show that the reliability is reduced with corrosion; the magnitude depends to a large extent on the modelling uncertainty used for the bond model for corroded reinforcement. The sensitivity analysis shows an influence of corrosion also on the sensitivities of the input parameters, which is expected based on the properties of the underlying bond model. This paper demonstrates that probabilistic evaluations give valuable insight of the reliability, which can be used to prolong the service-life of existing infrastructure and save both money and the environment.
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| 3. |
- Lundgren, Karin, 1968, et al.
(författare)
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Tests on anchorage of naturally corroded reinforcement in concrete
- 2015
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Ingår i: Materials and Structures. - : Kluwer Academic Publishers. - 1359-5997 .- 1871-6873. ; 48:7, s. 2009-2022
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Tidskriftsartikel (refereegranskat)abstract
- Many studies on the structural effects of corrosion in reinforcement have been conducted. However, most of them are based on artificially corroded test specimens. Thus, the knowledge available entails one major uncertainty, i.e. whether the results are reliable enough to be used for naturally corroded structures. The purpose of this study was to develop a test method and carry out experiments on naturally corroded specimens taken from an existing structure to investigate the anchorage capacity. Beam specimens were taken from the edge beams of a bridge at repair. The specimens showed corrosion-induced damage to a varying extent from no sign of corrosion to extensive cracking and spalling of the concrete cover. A four-point bending test indirectly supported by suspension hangers was chosen. The beams were strengthened with transverse reinforcement around the suspension hangers to avoid premature failure. Eight successful tests were carried out; in all these tests, diagonal shear cracks preceded a splitting induced pull-out failure; i.e. anchorage failure was achieved as intended. The results showed around 10 % lower capacity for the corroded specimens than for the reference ones. The average bond stress in the anchorage zone was estimated based on the applied load and available anchorage length. The stress was about 16 % lower in the beams with corrosion cracks, and 9 % lower in the beams with cover spalling compared to the reference specimens; there was also a larger variation among the damaged specimens than for the reference specimens. The results extend our knowledge concerning the structural behaviour of corroded reinforced concrete structures during field conditions.
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| 4. |
- Coronelli, Dario, et al.
(författare)
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FIB model code 2020 - Structural models for existing concrete structures
- 2018
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Ingår i: FIB 2018 - Proceedings for the 2018 fib Congress: Better, Smarter, Stronger. - 2617-4820. ; , s. 3019-3040
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Konferensbidrag (refereegranskat)abstract
- The paper gives an overview of this ambitious project, which builds upon the achievements of fib MC2010, the previous edition of the fib Model Code. MC2020 will deal with both the design of new structures and all the activities associated with the through-life management and care of existing concrete structures, including matters such as inservice assessment and interventions to extend the life / improve the performance of these structures. Particular attention will be paid to issues specific to existing structures. Relevant structural models are planned for the determination of their load capacity / structural reliability, serviceability, remaining service life etc taking account of: • Load-carrying behaviour not considered in design, such as compressive membrane action and the increase in concrete compressive strength with time due to ongoing hydration effects. • Load-carrying behaviour in deteriorated members and structures, which is different to those members which have not experienced deterioration. The paper gives consideration to corrosion of reinforced concrete members and prestressed concrete members, as well as to the effects of other forms of deterioration such as alkali-aggregate reactions and frost damage. The paper also notes some of the differences between the approaches employed for Life Cycle Assessment and Design (LCA / LCD) based on deterioration models, and the assessment of the present condition of the structure (i.e. at a given moment in time) which utilise mechanical models to represent the influences of the deterioration processes which are active.
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| 5. |
- Shu, Jiangpeng, 1987, et al.
(författare)
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Assessment of a cantilever bridge deck slab using multi-level assessment strategy and decision support framework
- 2019
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Ingår i: Engineering structures. - : Elsevier Ltd. - 0141-0296 .- 1873-7323. ; 200
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Tidskriftsartikel (refereegranskat)abstract
- A Multi-Level Assessment Strategy has previously been proposed and proved feasible for structural analysis of existing RC slabs. In this paper, the Multi-Level Assessment Strategy, which focuses on sophisticated structural analysis, was used to investigate the load-carrying capacity and structural behaviour of a composite bridge with an RC bridge deck slab subjected to a concentrated load. In addition to more sophisticated structural analysis, improved knowledge content about the structure and more advanced models for uncertainty consideration were also incorporated in a systematic way for higher levels of assessment. Furthermore, a decision support system was adopted, in which the cost for different alternatives regarding if and how the assessment should be enhanced with respect to model sophistication, knowledge content and modelling uncertainty were compared in a systematic way. The results show not only that the load-carrying capacity and the structural behaviour can be assessed with different level of detailing, but also that the cost for each level of assessment can be evaluated with a decision support system, facilitating more sustainable management of infrastructure.
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| 6. |
- Zandi, Kamyab, 1981, et al.
(författare)
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Ballastless Track – Minimizing the Climate Impact
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Railway transportation is becoming increasingly important for transport of passengers and goods in Sweden, Europe and many parts of the world. Ballastless (slab) railway systems are increasingly in use; however, their construction is known to cause a substantial climate impact. The objective of this study was to investigate possible methods to reduce greenhouse gas (GHG) emissions of slab tracks and to provide required knowledge to identify the methods with high potential for further development. The approach adopted in this study consists of two steps. First, a comprehensive literature study was carried out, including a survey of existing methods for reducing GHG emissions for slab tracks, and of those which require further research. These methods are presented and assessed with respect to criteria related to potential benefit, possibility to use in large volumes, quality assurance and cost. In the second step, recommendations are made on which of the different methods of reducing GHG emissions are suitable to further develop in future projects. Two uncertainties identified for all methods are related to quantification of potential benefits and the associated costs. Nonetheless, structural optimization of slab tracks is found to have potential to reduce the climate impact quite substantially, with the smallest risks associated. The most promising methods for structural optimization includes: geometry optimization to focus on the use of material where it is structurally most effective; stiffness optimization to reduce the energy consumption of trains; prestressing of concrete to minimize crack width; and employing steel fiber reinforced concrete to control cracks and reduce the use of traditional reinforcement. Three solutions combining these methods in different ways are suggested for future studies. Furthermore, methods related to the use of alternative binders & materials are also recommended to reduce the climate impact; however, it is noted that such methods in general exhibit larger uncertainties than structural optimization. Of the alternatives focusing on alternative binders & materials, the following were evaluated to be most promising: textile reinforcement, other cement types (e.g. CSA, BCSA & BYF cements) as well as optimized mix design of concrete. It is to be noted that the three suggested solutions based on structural optimization can also benefit from the use of alternative binders & materials. To sum up, combination of several methods is required to minimize the environmental impact, as in the suggested solutions. The needs for future investigation for each solution are also identified in the report. The project contributes to the overall goal of increasing consideration for the environment and climate by providing knowledge and road map on how GHG emissions can be reduced for slab tracks.
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| 7. |
- Akbarian, Mehdi, et al.
(författare)
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LCA+: Moving LCA into the Pavement Design Space
- 2012
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Ingår i: Proceeding of ACI International Convention.
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Konferensbidrag (refereegranskat)abstract
- The construction, operation, and maintenance of the United States roadway system are responsible for substantial energy and resource consumption. The current system of paved roads in the United States handles a volume of traffic on the order of 8 billion vehicle-miles per day. Due to high energy demand, road transport contributed the most greenhouse gases (GHGs) of any transportation mode in 2007, accounting for 83% of emissions from the transportation sector and 27% of all emissions in the United States. Improving the sustainability of this network requires better technical and decision making strategies starting with the design stage of pavements.While the Mechanistic-Empirical Pavement Design Guide (MEPDG) is being adopted as a design tool throughout the U.S. it lacks the ability to take into account the environmental impacts of pavement systems. Hence, it is necessary to incorporate the performance designs of MEPDG with an environmental assessment tool to merge the structural and environmental aspects of pavement design.The environmental impact of pavements throughout their lifetime is calculated using the life cycle assessment (LCA) technique. Conventional environmental assessments of pavements often overlook use phase related emissions, leading to conclusions based on incomplete results. Studies have empirically shown that an important factor in the life cycle assessment of pavements is the pavement-vehicle interaction (PVI) which describes the effect of pavement properties on vehicle fuel consumption. However, the results of these studies are not conclusive and cannot be generalized to all pavement designs.This research uses a mechanistic approach to rationalize PVI and creates a link between pavement properties and their impacts on fuel consumption. Moreover, a network-level analysis has been performed using the Long Term Pavement Performance (LTPP) program’s databases to calibrate and validate this model. Finally, life cycle assessment is taken into the design space by incorporating MEPDG designs with LCA principles, taking into account the effect of PVI over the pavement’s lifetime. Moreover, evaluation of high performance sustainable pavement systems is enabled by extending the realm of MEPDG to model-based LCA principles. Through this approach, pavement design is enhanced structurally and environmentally constructing the necessary foundations for LCA+.
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| 8. |
- Berg, F., et al.
(författare)
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Anchorage capacity of naturally corroded reinforcement in an existing bridge
- 2012
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Ingår i: Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Management, IABMAS 2012, Stresa, Lake Maggiore, 8-12 July 2012. - : CRC Press. ; , s. 2800-2807
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Konferensbidrag (refereegranskat)abstract
- Corrosion of reinforcement is one of the most common causes of deterioration in reinforced concrete bridges. Anchorage, prior to shear and bending moment resistance, is the main uncertainties in the evaluation of the structural behavior of corroded reinforced concrete bridges. Thus, to assess the remaining load-bearing capacity of deteriorated existing bridges, models to estimate the remaining bond and anchorage capacity are needed. Most of our knowledge on the structural behavior of corroded reinforced concrete structures is based on experimental investigations of artificially corroded concrete specimens. In this study, the anchorage capacity of naturally corroded steel reinforcement was investigated experimentally. The test specimens were taken from edge beams of a bridge, Stallbackabron, in Sweden. Since the dimensions and the amount of reinforcement were given on beforehand, it was only the test set-up which could be chosen freely. A test set-up consisting of a four point bending test indirectly supported with suspension hanger was considered to be the best alternative with the least disturbance and influence of the natural damages. Detailed design was done by using a non-linear finite element method. It was seen that the edge beams needed to be strengthened with transverse reiforcement, else they would have failed in a local failure at the suspension hole or in shear. The technique adopted for the strengthening was an internal mounting of steel reinforcement using epoxy as adhesive. The bond and anchorage behavior was examined in tests through measurements of applied load, free-end slip and mid-span deflection. A first test showed that additional measures were needed to ensure anchorage of the strengthening bars. In subsequent tests, they were therefore anchored at the top of the beam with hexagonal nuts and flat steel plates. In two following tests, the beams failed in a splitting induced pull-out failure, i.e. anchorage failure was achieved as wanted.
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| 9. |
- Blomfors, Mattias, 1990, et al.
(författare)
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Engineering bond model for corroded reinforcement
- 2018
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Ingår i: Engineering structures. - : Elsevier BV. - 0141-0296 .- 1873-7323. ; 156, s. 394-410
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion of the reinforcement in concrete structures affects their structural capacity. This problem affects many existing concrete bridges and climate change is expected to worsen the situation in future. At the same time, assessment engineers lack simple and reliable calculation methods for assessing the structural capacity of structures damaged by corrosion. This paper further develops an existing model for assessing the anchorage capacity of corroded reinforcement. The new version is based on the local bond stress-slip relationships from fib Model Code 2010 and has been modified to account for corrosion. The model is verified against a database containing the results from nearly 500 bond tests and by comparison with an empirical model from the literature. The results show that the inherent scatter among bond tests is large, even within groups of similar confinement and corrosion level. Nevertheless, the assessment model that has been developed can represent the degradation of anchorage capacity due to corrosion reasonably well. This new development of the model is shown to represent the experimental data better than the previous version; it yields similar results to an empirical model in the literature. In contrast to many empirical models, the model developed here represents physical behaviour and shows the full local bond stress-slip relationship. Using this assessment model will increase the ability of professional engineers to estimate the anchorage capacity of corroded concrete structures.
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| 10. |
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