| 1. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Samarbetsprojekt för effektivare brobyggande
- 2014
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Ingår i: Bygg & Teknik. - 0281-658X. ; 2014:7, s. 58-61
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Den svenska anläggningsbranschen har i ett flertal utredningar fått skarp kritik på grund av dålig produktivitet. Forskning visar på samma tendenser i övriga Europa och USA. Vissa mätningar tyder på att byggandet i den svenska anläggningsbranschen har en kostnadsökning som är dubbelt så hög jämfört med övriga branscher under de senaste 20 åren. Låg produktivitet och låg innovationsförmåga i byggbranschen leder till högre kostnader som inte garanterat ger en högre kvalitet. Trenden behöver vändas så att avkastningen på investeringar i vår infrastruktur ökar! Det första steget är att integrera konstruktions- och produktionsprocesserna, vilket ger kortare ledtider för både planering och uppförande av byggnadsverk. Onödigt långa byggtider orsakar störningar för andra aktörer i samhället.I ett pågående doktorandprojekt, som är ett samarbete mellan Trafikverket, WSP och Chalmers, söks möjligheten till att öka produktiviteten inom den svenska anläggningsbranschen. Huvudspåret är att utveckla och industrialisera brobyggandet. En effektivare byggindustri skapar möjligheter till att generera ett mervärde för samhället där mervärdet exempelvis kan motsvaras av att konstruktioner byggs med högre kvalitet till samma kostnad som idag alternativt samma eller högre kvalitet till en lägre kostnad än idag. Bortsett från rena kostnader bör naturligtvis en effektivare byggindustri också se till att lösningar väljs utifrån ett hållbart samhälle men med bibehållen fokus på produktivitet och innovation. En sådan lösning kan variera från själva processen till konstruktionsdetaljer.
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| 2. |
- Fang, Congqi, 1963, et al.
(författare)
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Bond behaviour of corroded reinforcing steel bars in concrete
- 2006
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 36:10, s. 1931-1938
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Tidskriftsartikel (refereegranskat)abstract
- The effect of steel corrosion on bond between steel bars and the surrounding concrete was investigated for different corrosion levels. Both pullout tests and finite element analysis were used and the results from the two were compared. An electrolyte corrosion technique was used to accelerate steel corrosion. For confined deformed bars, a medium level (around 4%) of corrosion had no substantial influence on the bond strength, but substantial reduction in bond took place when corrosion increased thereafter to a higher level of around 6%. It is demonstrated that the confinement supplied an effective way to counteract bond loss for corroded steel bars of a medium (around 4% to 6%) corrosion level. The results of finite element analyses, where it was assumed that rust behaved like a granular material, showed a reasonably good agreement with the experiments regarding bond strength and bond stiffness.
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| 3. |
- Fang, Congqi, 1963, et al.
(författare)
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Effect of corrosion on bond in reinforced concrete under cyclic loading
- 2006
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 36:3, s. 548-555
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Tidskriftsartikel (refereegranskat)abstract
- Cyclic loading can result in severe deterioration in the bond between reinforcing steel bar and the surrounding concrete, especially when the reinforcement is corroded. In this study, tests were carried out for bond stress-slip response of corroded reinforcement with concrete under cyclic loading. Parameters investigated include: corrosion level, confinement, bar type, and loading history. The results revealed that bond behaviour was significantly reduced under cyclic loading. Degradation in bond was significantly less for deformed bars than for smooth bars at the initial loading cycle, but the difference was diminished with loading. The bond reduction was more substantial for unconfined steel bars than for confined bars. The relatively high level of corrosion caused degradation primarily in the initial five cycles, the effect of corrosion being decreased with loading. It was also demonstrated that the cyclic bond stress-slip curves depended on loading history.
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| 4. |
- Fang, Congqi, 1963, et al.
(författare)
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The effect of corrosion on concrete bridges
- 2004
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Ingår i: Bridge Maintenance, Safety, Management and Cost / edited by Eiichi Watanabe, Dan M. Frangopol, Tomoaki Utsunomiya. - 9058096807
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Konferensbidrag (refereegranskat)
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| 5. |
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| 6. |
- Bagge, Niklas, 1987-, et al.
(författare)
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A multi-level strategy for successively improved structural analysis of existing concrete bridges: examination using a prestressed concrete bridge tested to failure
- 2019
-
Ingår i: Structure and Infrastructure Engineering. - : Informa UK Limited. - 1573-2479 .- 1744-8980. ; 15:1, s. 27-53
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes a multi-level strategy with increased complexity through four levels of structural analysis of concrete bridges. The concept was developed to provide a procedure that supports enhanced assessments with better understanding of the structure and more precise predictions of the load-carrying capacity. In order to demonstrate and examine the multi-level strategy, a continuous multi-span prestressed concrete girder bridge, tested until shear failure, was investigated. Calculations of the load-carrying capacity at the initial level of the multi-level strategy consistently resulted in underestimated capacities, with the predicted load ranging from 25% to 78% of the tested failure load, depending on the local resistance model applied. The initial assessment was also associated with issues of localising the shear failure accurately and, consequently, refined structural analysis at an enhanced level was recommended. Enhanced assessment using nonlinear finite element (FE) analysis precisely reproduced the behaviour observed in the experimental test, capturing the actual failure mechanism and the load-carrying capacity with less than 4% deviation to the test. Thus, the enhanced level of assessment, using the proposed multi-level strategy, can be considered to be accurate, but the study also shows the importance of using guidelines for nonlinear FE analysis and bridge-specific information.
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| 7. |
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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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Evaluation of safety formats for non-linear finite element analyses of statically indeterminate concrete structures subjected to different load paths
- 2016
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Ingår i: Structural Concrete. - : Wiley. - 1751-7648 .- 1464-4177. ; 17:1, s. 44-51
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Tidskriftsartikel (refereegranskat)abstract
- To increase the efficiency of new structures and perform safety evaluations of existing structures, it is necessary to model and analyse the non-linear behaviour of reinforced concrete. The applicability of the safety formats in present design codes is unclear for indeterminate structures subjected to loading in several directions. The safety formats in fib Model Code 2010 have been evaluated for a reinforced concrete frame subjected to vertical and horizontal loading and the influence of load history studied. Basic reliability methods were used together with response surfaces to assess the failure probabilities and one safety format did not meet the intended safety level. The results indicate the importance of load history and it is concluded that more research is required regarding how load history influences the safety level of complex structures.
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| 10. |
- Broo, Helén, 1968, et al.
(författare)
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A guide to non-linear finite element modelling of shear and torsion in concrete bridges
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Non-linear finite element (FE) analysis has become an important tool for structural design and assessment of reinforced concrete structures. When shear and torsion are limiting the capacity of a structure, three dimensional non-linear finite element methods often show higher load-carrying capacity compared to conventional analyses; therefore there is much to gain by using these methods, especially at assessment of existing structures. The reason for the higher capacities evaluated are mainly a more favourable load distribution when the structure is analysed in three dimensions and that the fracture energy associated with concrete cracking is included. In order to be able to use these higher capacities in reality, it is important that the modelling method is verified and to be aware of possible limitations. Recommendations are given concerning analysis methods and how a verification can be done, both concerning the capability of the program and concerning the actual FE model. Most important comments and recommendations are:•It is important to note that in FE programs commercially available today, beam elements cannot describe shear cracking and shear failure or reduced torsional stiffness due to cracking. The same applies for the out-of-plane shear in shell elements.•Most often in analysis of bridges, it is enough to assume full interaction between the reinforcement and the concrete. One exception is if the slip is important for the global response or the final failure, as if a shear failure takes place in a region where prestressing is anchored. Then the modelling should include slip between the steel and the concrete.•It is recommended that only the fracture energy of plain concrete is taken into account when defining the softening response of concrete, i.e. when the stress-strain relationship of the concrete is defined. This will yield results on the safe side; i.e. underestimation of the capacity and overestimation of deformations and crack widths.•It is often more stable to perform analyses using deformation control than load control. A method to enable deformation-controlled loading for several point loads by using a separate statically determined arrangement of stiff beams is described.Comments and recommendations are also given concerning how to model important details such as supports and connections, how different loading types can be considered, how to perform the analyses, how to evaluate the results through post-processing, and how to use the results in a safety format context.
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| 11. |
- Broo, Helén, 1968, et al.
(författare)
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Non-linear finite-element analysis of the shear response in prestressed concrete bridges
- 2009
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Ingår i: Magazine of Concrete Research. - : Thomas Telford Ltd.. - 0024-9831 .- 1751-763X. ; 61:8, s. 591 -608
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Tidskriftsartikel (refereegranskat)abstract
- For the structural assessment of concrete bridges, the non-linear finite-element method has become an important and increasingly used tool. The method has shown a great potential to reveal higher load-carrying capacity compared with conventional assessment methods. However, the modelling method used for reinforced and prestressed concrete members subjected to shear and torsion has been questioned. The aim of this study is to present an analysis method for evaluation of the load-carrying capacity of prestressed concrete bridges, when failure resulting from shear and torsion is the main problem. The modelling method used was previously worked out and verified for shear-type cracking and shear failure. Here, shell elements with embedded reinforcement were used together with non-linear material models, taking into account the fracture energy of cracking plain concrete and the reduction of the concrete compression strength owing to lateral tensile strain. Analyses with the method proposed have shown to predict the shear response and the shear capacity on the safe side. In the work presented here, the load-carrying capacity of a box-girder bridge was evaluated as a case study. The whole bridge was modelled, but only the part that was most critical to shear and torsion was modelled according to the method previously worked out and was combined with beam elements for the rest of the bridge. The case study showed a substantially higher load-carrying capacity for the bridge compared with the assessment with conventional methods. In the evaluation, several possible safety formats were used in combination with the non-linear finite-element method. It was shown that the format using partial safety factors gave unrealistic conservative results; it is more correct to use the semi-probabilistic formats for non-linear finite-element analysis. © 2009 Thomas Telford Ltd.
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| 12. |
- Broo, Helén, 1968, et al.
(författare)
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Reinforced and prestressed concrete beams subjected to shear and torsion
- 2007
-
Ingår i: Fracture Mechanics of Concrete and Concrete Structures. - 9780415440660 ; 2, s. 881-888
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Konferensbidrag (refereegranskat)abstract
- Today, the nonlinear finite element method is commonly used by practicing engineers, although design and assessment for shear and torsion in reinforced concrete structures are still made using methods based on sectional forces. By modelling the shear behaviour, using 3D nonlinear FEM, higher load carrying capacity and more favourable load distribution was shown, compared to conventional analysis. A modelling method using four-node curved shell elements with embedded reinforcement was evaluated in this study. Tests of reinforced and prestressed beams loaded in bending, shear and torsion were simulated. The increase in shear capacity, in addition to the reinforcement contribution, was modelled with a relationship for concrete in tension according to the modified compression field theory and compared with the use of a relationship related to the fracture energy of plain concrete. The results show that evaluations of the load-carrying capacity or crack width will be on the safe side, if only the fracture energy is used to define the concrete in tension.
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| 13. |
- Broo, Helén, 1968, et al.
(författare)
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Simulation of shear-type cracking and failure with non-linear finite element method
- 2007
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Ingår i: Magazine of Concrete Research. - : Thomas Telford Ltd.. - 0024-9831 .- 1751-763X. ; 59:9, s. 673-687
-
Tidskriftsartikel (refereegranskat)abstract
- Today, the non-linear finite element method is commonly used by practising engineers. Simulating the shear behaviour and shear failure of reinforced concrete structures, using three-dimensional non-linear finite element methods, has shown higher load-carrying capacity due to favourable load distribution, compared to conventional analyses. However, the modelling method for reinforced and prestressed concrete members subjected to shear and torsion has not been generally verified. Therefore, the method needs to be further investigated and confirmed to be practically reliable. The aim of this project is to develop, improve and verify a method to simulate the shear response of reinforced and prestressed concrete members. The method should be possible to use for large structures, for example box-girder bridges, subjected to various load actions. Experiments with panels loaded in shear and beams loaded in bending, shear and torsion are simulated by using non-linear FE analysis. The results showed that four-node curved shell elements with embedded reinforcement could simulate the shear response. It is well known that the shear sliding capacity is larger than what can be explained by the reinforcement contribution determined from a truss model. This increase is due to dowel action and aggregate interlock, and has been accounted for in the past by modifying the concrete tension response in models, e.g. according to the modified compression field theory. Results from the analyses show that without any modification, the capacity was underestimated and the average strains, i.e. the crack widths, were overestimated. On the other hand, if the concrete contribution to the shear capacity was considered with the expression from MCFT, the capacity was in many cases overestimated and the average strains underestimated.
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| 14. |
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| 15. |
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| 16. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Industrial bridge building- An effective bridge construction process through an integrated design and construction process
- 2014
-
Ingår i: Nordic Concrete Research. - 0800-6377. - 9788282080439 ; 2014:2, s. 79-82
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Konferensbidrag (refereegranskat)abstract
- This PhD-project aims to develop and industrialise bridge building, in order to achieve a more efficient and sustainable bridge construction process. The advancements of several key areas - materials science and technology, design and analysis methods, production techniques and information and communication technology - have resulted in a vast potential to rationalise the process and renew the designer's role. Initially, the project will define effective bridge construction criteria’s by means of interviews and case-studies. The work should result in an integrated design and production process. This project is a collaborative project, involving: Swedish Transport Administration, WSP and Chalmers.
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| 17. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Industrial bridge construction: Need for a more effective bridge construction process
- 2015
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Ingår i: The Eighth International Structural Engineering and Construction Conference, Sydney, Australia, November 23-28, 2015. - : ISEC Press. - 9780996043717 ; , s. 1115-1120
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Konferensbidrag (refereegranskat)abstract
- Designing for ease of construction is something that is always demanded by contractors and a challenge for the designers. It is widely known that the ability to influence a structure and its future properties is at its greatest in early stages, i.e. the project preparation phase followed by the design phase. Despite the fact that there is an obvious need for knowledge of construction in design work, there is a lack of a consistent and structured transmission of experience between the construction stage and the designing engineers. The results in this project are achieved based upon three standalone studies. A thorough literature review, a meta-analysis of the current research covering effective bridge construction and a study of the current industrial view on how the industry intend to achieve a more effective bridge building process. Based upon these studies it is clear that using a holistic approach and a production oriented design methodology is likely to generate the progress that the construction industry needs.
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| 18. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Integrated project team performance in early design stages – performance indicators influencing effectiveness in bridge design
- 2019
-
Ingår i: Architectural Engineering and Design Management. - : Informa UK Limited. - 1745-2007 .- 1752-7589. ; 15:4, s. 249-266
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Tidskriftsartikel (refereegranskat)abstract
- To create multi-functional and integrated project teams, and to adopt a team perspective in the early design stages, it is recognised in the literature that a more effective process is required; one that reduces the probability of costly changes and difficulties during construction. This paper presents an evaluation of project team collaboration during early design and development of construction documents for bridges in Sweden. The purpose was to study key variables influencing the performance of integrated project teams by using importance performance analysis (IPA). A self-evaluation questionnaire addressed clients, contractors, and structural engineering consultants in the Swedish bridge construction industry. The questionnaire addressed three essential cornerstones of value-creation during the engineering design process; culture, structure and competence. These were addressed at three organisational hierarchy levels, the organisation, project, and the individual level. Our results show that increased support and resources are required at the project level for better project team performance. Results further identify that project culture needs to be developed including both collaboration and social relationships as well as project competence, especially the ability to solve mutual issues. This research offers a ‘generalised’ and prioritised view of the challenges in the Swedish bridge construction industry in terms of creating integrated project teams.
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| 19. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Integrated project teams in early design stages - Key variables influencing cost effectiveness in bridge building
- 2016
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Ingår i: 19th IABSE Congress Stockholm, 21-23 September 2016, Challenges in Design and Construction of an Innovative and Sustainable Built Environment. ; , s. 598-606
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Konferensbidrag (refereegranskat)abstract
- The construction industry is usually regarded as a complex, multidisciplinary and project focused environment. It is also regularly identified as a one-of-a-kind nature, hence focus is on the uniqueness of projects rather than in similarities. The results presented in this article are based on questionnaire addressed to clients, contractors, and designers, mainly active within the Swedish infrastructure sector. The purpose is to highlight key-variables influencing cost effectiveness for the organization of integrated project teams, designing of projects, and construction at site. The results indicate that more attention needs to be paid to the actual project setting if to fully gain the benefits from integrated project teams. Further, the results indicates that it is mainly project culture; collaboration and social relationships, and project competence, the ability to solve mutual issues, that needs to be developed.
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| 20. |
- Ekström, Jonas, 1985, et al.
(författare)
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Influence of strain softening on spalling of concrete due to blast load
- 2014
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Ingår i: Nordic Concrete Research. ; 2/2014:50
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Konferensbidrag (refereegranskat)abstract
- A society needs a certain readiness for different emergency situations, such as explosions within the urban community but also civil safety shelter in the case of war. Therefore, the ability to evaluate and to strengthen existing buildings exposed to new demands is of great importance. Many experiments and numerical analyses indicate that structures of fibre reinforced concrete yield a more favourable response during dynamic load conditions compared to plain concrete. In this study the effects of spalling of a concrete wall subjected to blast loads were studied for plain concrete modelled with an elastic-plastic material model. The results from the analysis show that spalling occur when cyclic loading from a pressure wave gradually increase the plastic strains in the concrete.
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| 21. |
- Ekström, Jonas, 1985, et al.
(författare)
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Spalling in concrete subjected to shock wave blast
- 2016
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Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 122, s. 72-82
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies the response in a concrete wall subjected to shock wave blast, leading to spalling failure. This situation is important since spalled-off fragments in protective structures may cause severe injury to the persons or equipment it is supposed to protect. Many theoretical expressions indicates that spalling occurs when and where the tensile strength of a strain-softening material like concrete is reached regardless of the time duration of the applied load. By using a simple uni-axial numerical model, this study shows that spalling instead might occurs when the cyclic response from a blast wave gradually increase the inelastic strains in the concrete. This means that spalling takes place after several loading cycles and not necessarily at the depth where tensile strength is firstly reached. Furthermore, the study shows that the cyclic response in the material model used for numerical simulation has a decisive influence on the position and extent of the resulting spalling crack.
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| 22. |
- Fernandez, Ignasi, 1984, et al.
(författare)
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1D and 3D analysis of anchorage in naturally corroded specimens
- 2014
-
Ingår i: Proceedings of the 10th fib International PhD Symposium in Civil Engineering, Université Laval 21 – 23 July 2014, Québec, Canada. - 9782980676222 ; , s. 547-552
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Konferensbidrag (refereegranskat)abstract
- Corrosion of reinforcement causes cracking and spalling of concrete cover which affects the bond; this is a crucial factor in deterioration of concrete structures. Earlier, tests have been carried out on specimens with naturally corroded reinforcements; in this study, the focus is given to the modelling of these specimens. The aim was to evaluate the scope of simpler and more complex bond models to assess the structural behaviour. A comparison of two approaches to model the anchorage behaviour was done: (a) a one-dimensional analysis, where the bond-slip differential equation with a non-linear bond-slip constitutive model is numerically solved, and the mean bond strength as well as the required anchorage length to anchor the yield force are computed. (b) Finite element (FE) analyses were performed using 3D solid elements for concrete, and beam elements for reinforcement, where the interaction was explicitly described using the same bond-slip constitutive model as in approach (a). The results show differences between the two approaches. Each of the modelling alternatives had both drawbacks and advantages; while the more complicated model accounting for more variables led to more realistic results in comparison with observations, the simpler 1D analysis was very fast and efficient.
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| 23. |
- Gottsäter, Erik, et al.
(författare)
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Comparison of Models for the Design of Portal Frame Bridges with Regard to Restraint Forces
- 2017
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Ingår i: Structures Congress 2017, Denver, United States, 6-8 April 2017. - Reston, VA : American Society of Civil Engineers. - 9780784480403 ; , s. 326-339
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Konferensbidrag (refereegranskat)abstract
- In the design of concrete bridges an important aspect is limiting crack widths, since large cracks can lead to e.g. corrosion and affect the bridge functionality. Restraint forces caused by thermal loads and shrinkage will likely constitute a large part of the total forces acting on the bridge in crack width design. In this paper, restraint stresses in portal frame bridges are calculated according to Eurocode with simple hand calculation models, 2D frame models and linear elastic 3D FE-models. The results are then compared and used in Eurocode crack width design methods. Large tensile restraint stresses were found in the transverse direction close to the frame corners, and the required reinforcement amount significantly exceeded the minimum reinforcement prescribed by codes. The results are however unrealistic since the thermal load distribution is simplified, and the crack width formula does not take the reduction of restraint stresses due to cracking into account. Future studies shall therefore determine a more realistic thermal load distribution and the effects of cracking, in order to create a more accurate linear elastic 3D FE design method.
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| 24. |
- Gottsäter, Erik, et al.
(författare)
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Crack widths in base restrained walls subjected to restraint loading
- 2019
-
Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 189, s. 272-285
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Tidskriftsartikel (refereegranskat)abstract
- Cracks in concrete structures can have a negative impact on durability and aesthetic appearance. It is therefore important to estimate crack widths before construction, and to use suitable reinforcement amounts to limit crack widths. Crack widths are however hard to predict in restrained structures, as cracking reduces the stiffness, which in turn reduces the restraint and thereby the amount of cracking. In this paper, nonlinear finite element analyses of cracking are performed on base restrained walls mainly subjected to shrinkage. A non-linear material model for concrete and a bond-slip relation for concrete – reinforcement interaction are used. The model does not include the hardening process of concrete but instead applies the load effects on mature concrete, and is validated by comparisons with test results from full scale tests performed in previous research. Additionally, a sensitivity study is made to investigate the influence of certain parameters on crack widths and crack patterns. The intention is to use the model in the development of a model to be used in design of concrete structures which takes restraint effects into account in an improved, yet a simplified way. The results show that the model gives realistic crack patterns, but that it tends to overestimate crack widths and the number of cracks obtained. Therefore, the model is considered to be acceptable.
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| 25. |
- Gottsäter, Erik, et al.
(författare)
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Crack widths in portal frame bridges subjected to restraint effects
- 2019
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Ingår i: 20th Congress of IABSE, New York City 2019: The Evolving Metropolis - Report. ; , s. 1101-1105, s. 1101-1105
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Konferensbidrag (refereegranskat)abstract
- Restraint stresses appear in structural parts which are prevented from adjusting their shape when subjected to e.g. shrinkage or thermal actions. If the restrained stresses are large, cracking might occur, which can affect the durability of the structure. In the case of restraint effects, the reinforcement required in a bridge to limit the crack widths can be difficult to determine, as the magnitude of the restraint stresses depend on the stiffness of the structure. If cracking occurs, the stiffness is reduced and thereby also the stresses. For this reason, in structural parts affected by restraint effects, it can be hard to estimate both the number of cracks that will appear and the resulting restraint stress that governs the crack widths. In this study, crack widths in a portal frame bridge subjected to thermal actions and shrinkage were investigated using non-linear FE analysis. A bond-slip relation was used for concrete-reinforcement interaction, as the resulting crack spacing was unknown. Corresponding analysis was performed using linear elastic material models and hand calculations of crack widths, for two different thermal load cases, and relations between the results from the different methods are presented. The result can lead to the development of a more accurate design model, which would lead to more efficient use of reinforcement.
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| 26. |
- Gottsäter, Erik, et al.
(författare)
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Measurements and simulation of temperature in a portal frame bridge
- 2018
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Ingår i: IABSE Symposium, Nantes 2018: Tomorrow's Megastructures. - 9783857481611 ; , s. S24-9-S24-16
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Konferensbidrag (refereegranskat)abstract
- Since thermal loads can cause cracking, they are important to consider in bridge design. In order to evaluate and develop thermal load cases based on real simulations, models for simulating temperatures can be used. In this paper, a model for thermal simulation is used to simulate temperature in a portal frame bridge outside Lund, Sweden. The results are compared with temperature measurements in 13 locations in the same bridge, which were made during a 12-month period. The results show that although many important material parameters were unknown, the model could recreate both daily and seasonal temperature variations, although it tended to render temperatures about 1°C lower than the measurements, at least during summer. The model can be used in future work in determining thermal load values for the specific bridge type, assuming the model uncertainty is considered by e.g. adding 1°C to calculated load values.
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| 27. |
- Gottsäter, Erik, et al.
(författare)
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Simulation of thermal load distribution in portal frame bridges
- 2016
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Ingår i: IABSE Congress Stockholm, 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment.
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Konferensbidrag (refereegranskat)abstract
- Uneven exposure to e.g. solar radiation can cause temperature differences between various structural parts of a bridge, which leads to tensile stresses if the parts cannot move freely. In this study, thermal simulations and stress calculations on a model of a portal frame bridge are performed with the aim of evaluating the temperature difference between the bridge parts. It is shown that the temperature difference between parts which is proposed by Eurocode 1 is overestimated, thus the resulting stress distribution being unrealistic. Using the design method proposed by Eurocode 1 is therefore likely to exaggerate the required reinforcement in crack width limit design, which in turn would lead to unnecessary costs and environmental impacts. Further studies are needed in order to determine proper thermal load values and temperature distributions.
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| 28. |
- Gottsäter, Erik, et al.
(författare)
-
Simulation of thermal load distribution in portal frame bridges
- 2017
-
Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 143, s. 219-231
-
Tidskriftsartikel (refereegranskat)abstract
- Uneven exposure to e.g. solar radiation can cause temperature differences between various structural parts of a bridge, which leads to tensile stresses if the parts cannot move freely. In this study, thermal simulations and stress calculations on a model of a portal frame bridge are performed with the aim of evaluating the temperature difference between the bridge parts. Factorial design is used in a parametric study to determine the influence of different factors on the temperature difference and the largest reasonable temperature difference obtainable for the chosen weather data. The study shows that the quasi-permanent temperature difference between parts which is proposed by Eurocode 1 is overestimated, causing tensile stresses in the transverse direction to be exaggerated significantly. Using the design method proposed by Eurocode 1 is therefore likely to overestimate the required reinforcement in crack width limit design, which in turn would lead to unnecessary costs and environmental impacts. The results also indicate that the temperature distribution within the bridge is different from what is given in Eurocode load cases, and consequently, the largest tensile stresses appear in other areas of the bridge. A simplified temperature distribution is therefore investigated and shown to give similar results as the detailed thermal simulations.
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| 29. |
- Gottsäter, Erik, et al.
(författare)
-
Validation of Temperature Simulations in a Portal Frame Bridge
- 2018
-
Ingår i: Structures. - : Elsevier BV. - 2352-0124. ; 15, s. 341-348
-
Tidskriftsartikel (refereegranskat)abstract
- In the design of bridges, thermal loads are important to take into account since they can cause cracking if the structure or structural part is restrained from changing its size. Accurate thermal load values must therefore be used in bridge design, based on knowledge of the actual temperature distribution in the bridge. This paper presents the validation of a model for temperature simulation, to be used in future work in the determination of temperature differences between deck and abutments in portal frame bridges. The validation is performed by comparing simulated temperatures with temperatures measured at 13 locations in a portal frame bridge during a period of 12 months. The simulation model uses measured air temperature, wind speed and long- and short wave radiation as input to calculate the temperature for every hour in the time period, and includes the soil beside the bridge. The results show that the model was capable of predicting the temperature distribution adequately, and that conservative values of the temperature difference between the structural parts can be obtained by adding no more than a ΔT of 1.5 °C to the simulated temperature difference, depending on the application.
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| 30. |
- Honfi, Daniel, et al.
(författare)
-
Decision support for maintenance and upgrading of existing bridges
- 2017
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Ingår i: IABSE Conference, Vancouver 2017. - : International Association for Bridge and Structural Engineering (IABSE). - 9783857481536 ; , s. 336-345, s. 336-345
-
Konferensbidrag (refereegranskat)abstract
- Maintenance of transportation infrastructure assets can be relatively expensive, since it does not only include the direct cost of interventions, but also the indirect consequences of traffic disruptions. To make optimal decisions about maintenance actions, including rehabilitation and upgrading, reliable information about the performance of existing structures is needed. However, obtaining such information might require significant efforts and can be done in various ways. The purpose of an ongoing Swedish research project BIG BRO is to develop a framework for a decision support methodology that can be used for implementing maintenance strategies for bridges on a rational basis. The present paper provides a brief overview about the project as well as describes some of the ongoing work.
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| 31. |
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| 32. |
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| 33. |
- Jensen, Jens S., et al.
(författare)
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Guideline for load and resistance assessment of existing European railway bridges
- 2007
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Ingår i: Sustainable Bridges: Assessment for Future Traffic Demands and Longer Lives. - 9788371251610 ; , s. 221-230
-
Konferensbidrag (refereegranskat)abstract
- Many of the European railway bridges are getting close to the end of their service life. At the same time the railway operators demand higher axle loads for freight trains and higher speeds for passenger trains. This requires new and better approaches for assessing both the railway loads and the resistance of railway bridges. The main objective of the "Guideline for load and resistance assessment of existing European railway bridges" is to provide bridge evaluators with the most advanced knowledge regarding methods, models and tools that can be used in the assessment of existing railway bridges in order to get a realistic evaluation of their load carrying capacity and also more accurate evaluation of their remaining service life. This paper gives the general overview of the whole Guideline. Nevertheless, the major focus is placed on the innovative elements proposed in the Guideline, which have been developed due to several research activities performed within WP4.
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| 34. |
- Karlsson, Mats, 1953, et al.
(författare)
-
Methodology for selection of production method in an early stage - improved conceptual design process
- 2017
-
Ingår i: IABSE Conference, Vancouver 2017: Engineering the Future - Report. ; 109, s. 1879-1886
-
Konferensbidrag (refereegranskat)abstract
- The design of buildings and load carrying structures in early stages is a challenging task for a number ofreasons; scant information generally exists and several different requirements involving building structuresshould be managed, including technical, environmental and financial requirements. However, this phase ofthe design process is important and will fundamentally influence the following construction phase, as wellas the entire life of building structures. It is particularly important that the construction phase is properlyconsidered already in the design phase and that the production method selected is suitable for the designof building structures. The purpose of this research has been to improve the design process in theconceptual phase. The findings will highlight the benefits of design for production in bridge engineering.The aim has been to identify examples of practices and work methodologies that are of good caliber in theSwedish bridge construction sector. Early findings show that there exists a divergence between researchfindings and current practices. The research community has presented several participatory methodologiesfor the design process, such as Early Contractor Involvement (ECI) and Integrated Project Delivery (IPD) forthe potential of improving effectiveness in bridge engineering. However, studies of current practices inindustry show that these methodologies are difficult to implement and that there are hiddenconsequences. The processes developed should manage several requirements simultaneously, includingtechnical, environmental, health and safety, and financial. Competencies involved include StructuralEngineering, Architecture and Production Management, in addition to expertise in health and safety,materials science, environmental impact and procurement. Further, the intention is for the processes todeal with verification methods for the proposed conceptual solutions and risk analyses based on qualityassurance. Both new and existing building structures should be considered.
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| 35. |
- Lundgren, Karin, 1968, et al.
(författare)
-
3D Modelling of the bond behavior of naturally corroded reinforced concrete
- 2015
-
Ingår i: Extended abstract in “Residual Capacity of Deteriorated Concrete Structures” mini-seminar, 21st of April 2015, Oslo, Norway.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Corrosion of steel reinforcement causes cracking and spalling of concrete cover which affects the bond; this is a crucial factor in deterioration of concrete structures. Earlier, anchorage tests have been carried out on specimens with naturally corroded reinforcements. In an ongoing study, the focus is given to the modelling of thesespecimens. The aim is to evaluate the structural behaviour of the tested naturally corroded specimens. The analyses are performed in the FE program Diana. The frictional bond and corrosion models developed by Lundgren and Zandi are implemented in interface elements to model the interaction between the concrete and reinforcements. The preliminary results of the analysis showed differences in the shear crack pattern in comparison with the experiments. In the analysis, a longer remaining anchorage length was obtained in comparison with the experiment which resulted in a wrong failure mode. The issue might be related to the influence of aggregate interlock in FE analysis.
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| 36. |
- Lundgren, Karin, 1968, et al.
(författare)
-
Analyses of hollow core floors
- 2004
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- To obtain background information for code prescriptions for the shear and torsion interaction in hollow core floors, finite element analyses of some basic cases were made. A simplified global model for complete floors developed in Lundgren et al. (2004) was used, where the height of the hollow core units is included. Analyses where the longitudinal joints between the hollow core units were assumed to act as hinges were also carried out. Several set-ups were modelled, in total 30 floors. 12 floors with an even number of hollow core units (2, 4, and 6) were loaded with a point load on the joint in the centre of the floor. Furthermore, one example of each load case described in the Annex C in prEN 1168, was analysed. These examples include both line and point loads, and with and without a third line support. In all the analyses, the chosen span was 12 m, and the hollow core units were 400 mm high and 1200 mm wide.The analyses show that the maximum torsional moment was reduced when the height of the hollow core units was included in the analyses, compared to when hinges were assumed between the hollow core units. Also the bending moment was reduced, in most of the studied set-ups. This reduction was rather small. On the other hand, the shear force increased when the height of the hollow core units was included, especially the shear force at the supports.In four of the studied set-ups, a direct comparison to the present code, CEN/TC229 (2004), regarding the load distribution could be done. In CEN/TC229 (2004), it is not clear if the given distributions are valid for the bending moments at mid span or the shear forces at the supports. It is important to note that the distribution of these differ. No clear answer to which of these results that were considered in the code could be found.
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| 37. |
- Lundgren, Karin, 1968, et al.
(författare)
-
Analyses of two connected hollow core units
- 2004
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- To obtain background information for code prescriptions for the shear and torsion interaction in hollow core floors, finite element analyses of some basic cases were made. A simplified global model for complete floors developed in Lundgren et al. (2003) was used. A set-up with two simply supported hollow core units connected along a longitudinal joint and support of tie beams was modelled. The hollow core units were loaded with a point load situated at the longitudinal joint. Several parameters were varied; i.e. the section height, the slab length, an assumed gap in the longitudinal joint, stiffness of the tie beams, and the loading position. When the two hollow core units are loaded, they will deflect and rotate equally much, as there is symmetry. Therefore, no shear force will be transferred in the longitudinal joint. Compressive contact forces will appear at the upper edge of the longitudinal joint, while the lower edge of the longitudinal joint will open without any force transfer. The main studied result from the analyses is the distribution of the contact forces along the upper edge of the longitudinal joint. The results show that the contact forces in the longitudinal joint had typically a peak where the point load was applied. When no gap was assumed in the longitudinal joint and the tie beams were assumed to be infinitely stiff, compressive contact forces appeared towards the supports, almost in triangular shaped blocks. These blocks decreased and vanished when the stiffness of the tie beams decreased, and also when there was a gap in the longitudinal joint.In the analyses where a gap was assumed in the longitudinal joint between the hollow core units, no contact is obtained for low loads. After a certain load, contact is obtained, and the contact forces between the hollow core units start to act. This load can be predicted by hand calculations.As the analyses are non-linear, the results from various load cases can not be super positioned. This was demonstrated in one example. In the studied set-up with only two hollow core units, the deflections in horizontal bending were of the same magnitude as the deformations due to torsional rotations. Therefore, very small reductions in torsional moments were observed. The torsional moments would most likely be more reduced if floors with more hollow core units were studied.
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| 38. |
- Lundgren, Karin, 1968, et al.
(författare)
-
Anchorage of corroded reinforcement – from advanced models to practical applications
- 2015
-
Ingår i: . Extended abstract in “Residual Capacity of Deteriorated Concrete Structures” mini-seminar, 21st of April 2015, Oslo, Norway.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- When reinforcement in concrete corrodes, splitting stresses around corroded bars may lead to cover cracking and even cover spalling, affecting the anchorage. The aim of this paper is to give an overview on both advanced and practical models for anchorage capacity of corroded reinforcement which have been developed at Chalmers, and to show how these models can be applied in the assessment of existing bridges. The application of the practical model isexemplified in assessment of two bridges built in the 1960s. The bridges exhibit systematic damage in the form of spalled concrete on the bottom side of the main beams at cast joints where large amounts of reinforcement are spliced. The anchorage length needed to anchor theyield force was calculated from the bond-slip response, using the one-dimensional bond-slip differential equation. The model proved to be easy to use in practical design work.Furthermore, the bridges could be shown to have sufficient capacity, and costly strengthening could be avoided. This work clearly demonstrates the potential to certify sufficient loadcarrying capacity of corroded reinforced concrete structures through improved models.
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| 39. |
- Lundgren, Karin, 1968, et al.
(författare)
-
Tests on anchorage of naturally corroded reinforcement in concrete
- 2015
-
Ingår i: Materials and Structures. - : Kluwer Academic Publishers. - 1359-5997 .- 1871-6873. ; 48:7, s. 2009-2022
-
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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| 40. |
- Lundgren, Karin, 1968, et al.
(författare)
-
The effect of corrosion on bond in reinforced concrete
- 2006
-
Ingår i: Proceedings “European Symposium on Service Life and Serviceability of Concrete Structures ESCS-2006. ; , s. 252-257
-
Konferensbidrag (refereegranskat)abstract
- When reinforcement in concrete corrodes, splitting stresses are induced in the concrete. Thereby, the bond between the reinforcement and the concrete is influenced. This effect has been studied both experimentally and theoretically by many researchers. Here, this is investigated and described in a systematic way. An overview of the effect for various cases is given. Parameters defining the various cases are reinforcement type, existence of transverse reinforcement, and confinement due to concrete and boundaries. Preliminary recommendations for assessment of existing structures are given.
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| 41. |
- Lundgren, Karin, 1968, et al.
(författare)
-
Är förankringskapaciteten tillräcklig i broar med rostande armering?
- 2012
-
Ingår i: Bygg & Teknik. - 0281-658X. ; 104:7, s. 17-19
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- I denna studie har förankringskapaciteten för naturligt korroderad armering undersökts experimentellt. Provkropparna som använts är från kantbalkar på Stallbackabron i Trollhättan. Balkarna uppvisar olika grad av korrosionsskador, från inga tecken alls på korrosion, till omfattande sprickor och täckskiktsspjälkning. Balkarna provades i fyrpunktsböjning, upphängda med indirekta stöd. Vid belastning erhölls förankringsbrott efter att sneda skjuvsprickor bildats. Vid försöket mättes last, ändglidning och nedböjning. Försöksresultaten skall användas för att öka vår kunskap om verkningssätt och bärförmåga hos betongkonstruktioner med korroderad armering. Framförallt kompletterar den tidigare kunskap inom området genom att korrosionen har skett på naturligt sätt.
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| 42. |
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| 43. |
- Olofsson, Ingvar, 1943, et al.
(författare)
-
Sustainable Bridges: Tillämpning av erfarenheter från ett EU-projekt
- 2005
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the present project is to systematically collect, analyse and maintain knowledge about the demography of the present European stock of railway bridges and of its weaknesses and identified problems. The intention is to further analyse, develop and use this knowledge as a basis for improved design and construction methods of new bridges in Sweden, railway bridges as well as road bridges. Basic background data is collected within the European project Sustainable Bridges, funded by the European Commission within its sixth framework programme, where the project members are actively participating in areas of strategic importance. Background data regarding the Swedish bridges is collected also through the recently launched Swedish bridge management system BaTMaN, which is developed, owned and managed by the Swedish Road Administration and The Swedish Railway Authorities.The results of the present project (enhanced methods for design, improved detailing, proposals for amendments to standards etc) may be directly applied by contractors and design consultants and will be beneficial to the end users of the products, i.e. the owners of the bridges.The activities within Sustainable Bridges have, since the project started 1st of December 2003, been focused on a superficial identification of lack of knowledge, as defined by the European railway owners. A mapping of the European bridge demography has been carried out and is reported together with a specification of the most frequent problems of the existing bridges. Development work for enhanced assessment methods and improved methods for inspection and monitoring of the bridges has started. In the next phases of Sustainable Bridges the activities will be concentrated on the identified problem areas and the degree of detailing will at the same time be increased.The identified problem areas, as specified by the European railway owners, appear to be very similar to the needs of the Swedish bridge owners in spite of the fact that the studied bridges are geographically distributed over all Europe and its major climate zones. The same conclusion is valid for the defined improvement areas. It may therefore be assumed that the results achieved within Sustainable Bridges will be highly relevant for further development and application also to Swedish bridges and to the construction of new Swedish bridges.This report is the first report in a series of four reports, which will be produced over a period of four years, provided that continued funding is raised.
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| 44. |
|
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| 45. |
- Olofsson, Ingvar, 1943, et al.
(författare)
-
Sustainable Bridges: Tillämpning av erfarenheter från ett EU-projekt, slutrapport
- 2008
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the project was to systematically collect and analyse knowledge about the weaknesses and identified problems of the present European stock of railway bridges. The intention was to further analyse, develop and use this knowledge as a basis for improved design and construction methods of new bridges in Sweden, railway bridges as well asroad bridges.Basic background data is collected within the European project “Sustainable Bridges”, funded by the European Commission within its sixth framework programme, where the project members are actively participating in areas of strategic importance. Background data regarding the Swedish bridges is collected also through the recently launched Swedish bridge management system BaTMan, which is developed, owned and managed by the Swedish Road Administration and The Swedish Railway Authorities. The system is not a final system and some suggestions for improvement are presented.The results of the present project (enhanced methods for design and construction, improved detailing, proposals for amendments to standards etc) may be directly applied by contractors and design consultants and will be beneficial to the end users of the products, i.e. the owners of the bridges. The activities within “Sustainable Bridges” were started 1st of December 2003, with a superficial identification of “lack of knowledge”, as defined by the European railwayowners. A mapping of the European bridge demography was carried out and reported together with a specification of the most frequent problems of the existing bridges. Development work for enhanced assessment methods and improved methods for inspection and monitoring of the bridges followed. In the final phases of “Sustainable Bridges” the activities were concentrated on the identified problem areas and the degree of detailing was at the same time increased.The identified problem areas, as specified by the European railway owners, appear to be very similar to the needs of the Swedish bridge owners in spite of the fact that the studied bridges are geographically distributed over all Europe and its major climate zones. The same conclusion is valid for the defined improvement areas. The results achieved within “Sustainable Bridges” are therefore highly relevant for further development and application also to Swedish bridges and to the design and construction of new Swedish bridges.
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| 46. |
- Pacoste, Costin, et al.
(författare)
-
Recommendations for finite element analysis for the design of concrete slabs
- 2012
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In the bridge design community the usage of 3D finite element analyses has increased substantially in the last few years. Such analyses provide the possibility for a more accurate study of the structure than what is possible by using more traditional design tools. However, in order to use the full strength of the finite element method in daily design practice a number of critical issues have to be addressed. These issues are related either to the FE-modeling itself (geometry, support conditions, mesh density, etc.) or to the post processing of the obtained results (stress concentrations, choice of critical sections, distribution widths and so on). The purpose of this report is to address these problems and provide recommendations and guidelines for the practicing engineers.The recommendations given here are based on what was found in literature combined with engineering judgement and considerations from engineering practice. The recommendations are believed to be conservative, implicating a potential for improvement based on increased knowledge on the response and distribution of shear in concrete slabs and how this is reflected by linear FE analysis. This also means that, in many cases, there may be other alternatives that are equally correct as the ones suggested in this report.
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| 47. |
- Plos, Mario, 1963, et al.
(författare)
-
A multi-level structural assessment strategy for analysis of RC bridge deck slabs
- 2016
-
Ingår i: IABSE Congress Stockholm 2016. - : IABSE c/o ETH Hönggerberg. - 9783857481444 ; , s. 1559-1566, s. 1564-1571
-
Konferensbidrag (refereegranskat)abstract
- A multi-level structural assessment strategy for evaluation of response and load carrying capacity of reinforced concrete bridges deck slabs are presented [1]. The strategy is based on the principle of successively improved analysis methods in structural assessment. It provides a structured approach to the use of simplified as well as advanced non-linear finite element analysis methods. The proposed methods were used for analysis of previously tested slabs subjected to bending and shear type of failures. As expected, the advanced methods gave an improved understanding of the structural response and were capable of demonstrating higher, yet conservative, predictions of the load-carrying capacity. The proposed strategy clearly provides the engineering community a framework for using successively improved structural analysis methods for enhanced assessment in a straightforward manner.
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| 48. |
- Plos, Mario, 1963, et al.
(författare)
-
A multi-level structural assessment strategy for reinforced concrete bridge deck slabs
- 2017
-
Ingår i: Structure and Infrastructure Engineering. - : Taylor & Francis. - 1573-2479 .- 1744-8980. ; 13:2, s. 223-241
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a multi-level assessment strategy for reinforced concrete bridge deck slabs. The strategy is based on the principle of successively improved evaluation in structural assessment. It provides a structured approach to the use of simplified as well as advanced non-linear analysis methods. Such advanced methods have proven to possess great possibilities of achieving better understanding of the structural response and of revealing higher load-carrying capacity of existing structures. The proposed methods were used for the analysis of previously tested two-way slabs subjected to bending failure and a cantilever slab subjected to a shear type of failure, in both cases loaded with concentrated loads. As expected, the results show that more advanced methods yield an improved understanding of the structural response and are capable of demonstrating higher, yet conservative, predictions of the load-carrying capacity. Nevertheless, the proposed strategy clearly provides the engineering community a framework for using successively improved structural analysis methods for enhanced assessment in a straightforward manner.
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| 49. |
- Plos, Mario, 1963
(författare)
-
Application of Fracture Mechanics to Concrete Bridges. Finite element analyses and experiments
- 1995
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Material models based on fracture mechanics together with non-linear finite element analyses have been used in combination with experiments to study the behaviour of reinforced concrete bridges. The work covers two aspects of interest in the design of concrete bridges.* The shear behaviour was studied in full-scale tests on two highway bridges. The capacities of the bridges were compared with the shear capacities according to the design model in the Swedish concrete code. Non-linear finite element analyses were performed on one of the bridges tested.* The reinforcement detailing in frame corners was studied and the alternative of splicing the reinforcement within the corners of a frame bridge was examined in three test series. Non-linear finite element analyses were performed for some of the specimens tested. The objective of the study was to obtain greater knowledge of the behaviour of concrete bridges for these two aspects, as well as to find out how analyses based on fracture mechanics can be used to improve understanding of this behaviour. A background to the fracture mechanics for concrete and to the models used in the analyses is given. The results of the full-scale shear tests indicate that the design model for shear can predict the capacity for typical shear failures. However, when a combination of shear and moment actions leads to failure, the test results revealed shortcomings in the design models in the Swedish concrete code. A finite element analysis based on the discrete crack approach was performe d successfully up to initiation of the final failure; the analysis showed that the inclined crack leading to failure was initiated at mid-height of the bridge slab. The tests on frames and frame corners included both monotonic and cyclic loading. Reinforcement detailing suitable for portal frame bridges, and also detailing suitable for civil defence shelters, was studied. The test results did not uncover any drawbacks related to splicing of the reinforcement in the frame corners. Some of the test specimens were analysed using a material model for concrete based on fracture mechanics and the smeared crack approach. The finite element analyses were found to reflect the mechanical behaviour of the specimens tested throughout the failure process; the analysis results were in good agreement with the test results. The results from both the analyses and the tests support the idea that it should be feasible to splice the reinforcement within the corner area of a frame bridge. The use of fracture mechanics and non-linear finite element analyses has been shown to be a most powerful tool which, together with a limited number of tests, can increase understanding of the failure process in reinforced concrete structures.
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| 50. |
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