| 1. |
- Enochsson, Ola, et al.
(författare)
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Assessment and condition monitoring of a concrete railway bridge in Kiruna, Sweden
- 2006
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Ingår i: Bridge maintenance, safety, management, life-cycle performance and cost. - London : Taylor and Francis Group. - 0415403154
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Konferensbidrag (refereegranskat)abstract
- A two-span railway concrete trough bridge over Luossajokk in Kiruna in northern Sweden has been studied. The owner wanted to increase the axle loads from 250 to 300 kN in order to reduce freight costs for iron ore. Examples are given of methods used and results obtained from the assessment where bending, shear and fatigue were studied. Material properties, loads and load carrying capacity were evaluated using deterministic and probabilistic methods. It was shown that the bridge could carry the higher loads with a safety index β > 4.7 for reasonable assumptions of the load distributions. A measurement system was installed to check the actual level of critical strains and the worst positions of the train. Results are also given from a condition monitoring program 2001-2006, launched to periodically check the development of strains with time.
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| 2. |
- Bagge, Niklas, 1987-, et al.
(författare)
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Assessment of concrete bridges - Prestress forces : Experiences from full-scale testing to failure of a bridge in Kiruna
- 2017
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Ingår i: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation. - Oslo : Nordic Concrete Federation. ; , s. 267-270
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Konferensbidrag (refereegranskat)abstract
- To calibrate methods for condition assessment of prestressed concrete (PC) bridges, tests were carried out on a 55 year old five-span bridge with a length of 121 m in Kiruna in northern Sweden. Both non-destructive and destructive full-scale tests were performed. This paper presents results regarding the residual forces in the prestressed reinforcement.
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| 3. |
- Bell, Brian, et al.
(författare)
-
Sustainable Bridges – Past and Future. Reflections on a European Project 2003 – 2007
- 2023
-
Ingår i: IABSE Congress 2023 New Delhi, Engineering for Sustainable Development. - : International Association for Bridge and Structural Engineering. ; , s. 690-698
-
Konferensbidrag (refereegranskat)abstract
- Twenty years ago, in 2003, a European project was started to increase the sustainability of existing railway bridges. This paper summarises what was achieved and looks ahead. Nine Working Packages were organized: (1) Background material; (2) Guidance by stakeholders; (3) Condition Assessment and Inspection Guidelines; (4) Loads, Capacity and Resistance Guidelines; (5) Monitoring Guidelines; (6) Repair and Strengthening Guidelines; (7) Demonstration with Field testing of Bridges; (8) Demonstration on Monitoring on Bridges; and (9) Training and Dissemination.Some of the main results (from 4 Guidelines and 47 Background documents) are highlighted and some experiences, conclusions and thoughts about the future are given. Hidden strengths and weaknesses are discussed, analyses and codes for assessment can be improved, new monitoring and strengthening methods are available and life length can be prolonged.
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| 4. |
- Blanksvärd, Thomas, et al.
(författare)
-
Test to failure of a steel truss bridge – Calibration of assessment methods
- 2014
-
Ingår i: Bridge Maintenance, Safety, Management and Life Extension. - London : CRC Press, Taylor & Francis Group. - 9781138001039 - 9781315760698 ; , s. 1076-1081
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Konferensbidrag (refereegranskat)abstract
- The steel truss railway bridge at Åby River was built in 1957 with a span of 32 m (105 feet). In 2012 it was replaced by a new steel beam bridge and the old bridge was placed beside the river. It was tested to failure to study its remaining load-carrying capacity in September 2013. The test was carried out by Luleå University of Technology by commission from Trafikverket as a part of the European Research Project MAINLINE (www.mainline-project.eu). In this paper some preliminary results are given. Two hydraulic jacks, anchored by cables to the bedrock, pulled the bridge downwards. The bridge remained elastic up to about three times the original design load and the load could then be almost doubled with substantial yielding deformations before a buckling failure appeared in the top girders for a load of ca. 11 MN (1000 short tons) for a midpoint deflection of ca. 0, 2 m (8 inches). No brittle or fatigue failure in any of the joints appeared and the bridge proved to behave in a ductile way with a substantial hidden capacity.
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| 5. |
- Elfgren, Lennart, 1942-, et al.
(författare)
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Load-testing used for quality control of bridges
- 2018
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Ingår i: Quality Specifications for Roadway Bridges. ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Load testing is a way to control the capacity and function of a bridge. Methods and recommendations for load testing are described and examples are given form tests carried out. In order not to damage the bridge being tested, the load must be limited, often to be within the serviceability limit state (SLS). Numerical models can be calibrated by load tests and then be used to check the carrying capacity for higher loads than what has been tested. Need for further work and recommendations are discussed. By effective planning costs can be saved and a more sustainable use of bridges can be obtained.
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| 6. |
- Elfgren, Lennart, et al.
(författare)
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Sustainable railway bridges with higher axle loads : monitoring examples from northern Sweden
- 2007
-
Ingår i: High Tech in Heavy Haul. - Luleå : Luleå tekniska universitet. - 9789163306075 ; , s. 159-166
-
Konferensbidrag (refereegranskat)abstract
- Monitoring of several railway bridges has been carried out in northern Sweden in order to increase the allowable axle load. The work is part of a European Integrated Project "Sustainable Bridges - Assessment for Future Traffic Demands and Longer Lives". The paper describes the project and gives some examples of applications.
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| 7. |
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| 8. |
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| 9. |
- Nilimaa, Jonny, 1986-, et al.
(författare)
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Assessment and Loading to Failure of Three Swedish RC Bridges
- 2018
-
Ingår i: Evaluation of Concrete Bridge Behavior through Load Testing. - Faarmington Hills, MI : American Concrete Institute. - 9781641950077 ; , s. 8.1-8.18
-
Bokkapitel (refereegranskat)abstract
- Current codes often underestimate the capacity of existing bridges. The purpose of the tests presented here has been to assess the real behaviour and capacity of three types of bridges in order to be able to utilize them in a more efficient way.The three studied bridges are: (1) Lautajokk – A one-span trough bridge tested in fatigue to check the shear capacity of the section between the slab and the girders; (2) Övik – A two span trough bridge strengthened with Near Surface Mounted Reinforcement (NSMR) of Carbon Fibre Reinforced Polymers (CFRP) tested in bending, shear and torsion; and (3) Kiruna – A five-span prestressed three girder bridge tested to shear-bending failures in the girders and in the slab.The failure capacities were considerably higher than what the code methods indicated. With calibrated and stepwise refined finite element models, it was possible to capture the real behaviour of the bridges. The experiences and methods may be useful in assessment and better use of other bridges.
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| 10. |
- Nilimaa, Jonny, et al.
(författare)
-
Extend the life of existing railway bridges : Results from EU FP7 project MAINLINE
- 2015
-
Ingår i: IABSE Conference Geneva 2015. - Geneva : International Association for Bridge and Structural Engineering. - 9783857481406 ; , s. 1219-1226
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There is a need to extend the life and capacity of many existing bridges. One of the objects of the EU FP7 Project MAINLINE, 2011-2014, was to facilitate this. Guidelines for assessment and strengthening methods are presented as well as case studies in which existing bridges are studied in order to extend their life length. One example is the prestressing of the slab in a one-span concrete trough bridge in order to increase its load-carrying capacity. Horizontal holes were drilled trough the slab and in them steel bars were placed and post-tensioned. In this way a compressive stress was introduced into the concrete section so that it’s bending and shear capacity was increased.In another study a metal truss bridge was monitored in order to check strain and stress ranges in critical connections to enable an enhanced evaluation of the remaining fatigue resistance. The studied bridge was then replaced and loaded to failure to study its robustness and the reliability of applied assessment methods. The results could then be applied to prolong the life of an identical twin bridge located in the northern part of Sweden. A Life Cycle Assessment Tool (LCAT) has been developed to enable Infrastructure Managers to choose optimal maintenance strategies.
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| 11. |
- Nilimaa, Jonny, et al.
(författare)
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Extended Life of Railway Bridges. Results from EC-FP7-project MAINLINE
- 2013
-
Ingår i: Assessment, Upgrading and Refurbishment of Infrastructures. - Zürich : International Association for Bridge and Structural Engineering. - 9783857481239 ; , s. 314-315
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Konferensbidrag (refereegranskat)abstract
- There is a need to extend the life of many existing railway bridges. To facilitate this is one of the objects of the EC-FP7-Project MAINLINE, covering a period from 2011 to 2014. Three case studies are presented in which existing bridges are being studied in order to extend their life length: First a concrete trough bridge strengthened with post stressed bars in drilled holes through the slab is considered; followed by another concrete trough bridge strengthened with sawn in Near Surface Mounted Reinforcement (NSMR) of Carbon Fibre Reinforce Polymers (CFRP); and finally a steel truss bridge which will be loaded to failure to calibrate the assessment methods.
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| 12. |
- Nilimaa, Jonny, et al.
(författare)
-
Extending the life of elderly rail bridges by strengthening
- 2014
-
Ingår i: Bridge Maintenance, Safety, Management and Life Extension. - London : CRC Press, Taylor & Francis Group. - 9781138001039 - 9781315760698 ; , s. 1082-1088
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Konferensbidrag (refereegranskat)abstract
- There is a need to extend the life of many existing railway bridges. To facilitate this is one of the objects of the EC-FP7-Project MAINLINE, covering a period from 2011 to 2014. New or improved technologies are investigated to help with this. For bridges, the most promising techniques are enhanced inspection, assessment and strengthening methods. Case studies are presented where three different strengthening techniques have been applied to existing concrete trough bridges. First, sawn in Near Surface Mounted Reinforcement (NSMR) of Carbon Fibre Reinforce Polymers (CFRP) are used; followed by a bridge where carbon fibre cables were drilled through the bridge and finally a bridge was strengthened with post tensioned bars in drilled holes through the slab in the transverse direction. All three methods proved to be very successful.
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| 13. |
- Nilimaa, Jonny, et al.
(författare)
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Maintenance and Renewal of Concrete Rail Bridges - Results from EC project MAINLINE
- 2014
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 50, s. 25-28
-
Tidskriftsartikel (refereegranskat)abstract
- There is a need to extend the life and capacity of many existing railway bridges. One of the objects of the EC-FP7-Project MAINLINE, 2011-2014, is to facilitate this. Guidelines for assessment and strengthening methods are presented as well as case studies in which existing bridges are being studied in order to extend their life length. Case studies on bridges tested to failure in order to calibrate assessment methods are also presented. Fatigue is often a vital question. A Life Cycle Assessment Tool (LCAT) is being prepared to enable Infrastructure Managers to choose optimal maintenance strategies.
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| 14. |
- Olofsson, Ingvar, et al.
(författare)
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Assessment of European railway bridges for future traffic demands and longer lives : EC project "sustainable bridges"
- 2005
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Ingår i: Structure and Infrastructure Engineering. - : Informa UK Limited. - 1573-2479 .- 1744-8980. ; 1:2, s. 93-100
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Tidskriftsartikel (refereegranskat)abstract
- A European Integrated Research Project has recently been started within the 6th Framework Program of the European Commission. The project aims at improved methods for the upgrading of existing railway bridges within the European railway network. The main objectives of the project are to increase the transport capacity by allowing higher axle loads and by increasing the maximum speeds. Other objectives are to increase the residual lifetime of existing bridges and to enhance management, strengthening and repair systems. The overall goal is to enable the delivery of improved capacity without compromising the safety and economy of the working railway. A consortium consisting of railway bridge owners, consultants, contractors, research institutes and universities carry out the project, having a gross budget of more than 10 million Euros. Funding from the European Commission covers a major portion of the four-year project costs
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| 15. |
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| 16. |
- Paulsson, Björn, et al.
(författare)
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Sustainable bridges : results from a European integrated project
- 2010
-
Ingår i: Large structures and infrastructures for environmentally constrained and urbanised areas. - Zurich : International Association for Bridge and Structural Engineering. - 9783857481222
-
Konferensbidrag (refereegranskat)abstract
- In Europe there are more than 1 million bridges, many of them older than 50 years and quite a few of the railway bridges even have an age of more than100 years. These bridges represent a large value. Often there is a wish to increase speed and loads on existing bridges and then the question is if a bridge can be strengthened to fulfil the demands, or if it has to be replaced with a new one? This was the background for a European integrated research project within the 6th Framework Programme named "Sustainable Bridges". The project was carried out between 2003 and 2007 with 32 partners from 12 countries and with a gross budget of more than 10 million Euros. The aim of the project was to help to increase the use of the European railway network. For bridges, this can only be achieved by allowing higher axle loads on freight vehicles and by increasing the maximum permissible speed of passenger trains. In turn, any strengthening or maintenance work on the existing bridge stock to help in meeting this challenge must be undertaken without causing unnecessary disruption to the carriage of passengers and goods, and without compromising the safety and economy of the working railway. The project has developed many background documents and the following four major guidelines:(a) Inspection and Condition Assessment of Railway Bridges (b) Load and Resistance Assessment of Railway Bridges (c) Monitoring of Railway Bridges (d) Repair and Strengthening of Railway Bridges The results have been tested and demonstrated on several bridges in order to promote better engineering solutions which may produce savings throughout Europe. In the paper reflections on the efficiency and dissemination of the project will be given as well as examples of results and how they now are implemented. All major results from the project are available at the website http://www.sustainablebridges.net/.
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| 17. |
- Puurula, Arto, et al.
(författare)
-
Assessment of the Strengthening of an RC Railway Bridge with CFRP utilizing a Full-Scale Failure Test and Finite-Element Analysis
- 2015
-
Ingår i: Journal of Structural Engineering. - 0733-9445 .- 1943-541X. ; 141:1
-
Tidskriftsartikel (refereegranskat)abstract
- A finite element (FE) model was calibrated using the data obtained from a full-scale test to failure of a 50 year old reinforced concrete (RC) railway bridge. The model was then used to assess the effectiveness of various strengthening schemes to increase the loadcarrying capacity of the bridge. The bridge was a two-span continuous single-track trough bridge with a total length of 30 m, situated in Örnsköldsvik in northern Sweden. It was tested in situ as the bridge had been closed following the construction of a new section of the Railway line. The test was planned to evaluate and calibrate models to predict the load-carrying capacity of the bridge and assess the strengthening schemes originally developed by the European research project called Sustainable bridges. The objective of the test was to investigate shear failure, rather than bending failure for which good calibrated models are already available. To that end, the bridge was strengthened in flexure before the test using near-surface mounted square section carbon fiber reinforced polymer (CFRP) bars. The ultimate failure mechanism turned into an interesting combination of bending, shear, torsion, and bond failures at an applied load of 11.7 MN (2,630 kips). A computer model was developed using specialized software to represent the response of the bridge during the test. It was calibrated using data from the test and was then used to calculate the actual capacity of the bridge in terms of train loading using the current Swedish load model which specifies a 330 kN (74 kips) axle weight. These calculations show that the unstrengthened bridge could sustain a load 4.7 times greater than the current load requirements (which is over six times the original design loading), whilst the strengthened bridge could sustain a load 6.5 times greater than currently required. Comparisons are also made with calculations using codes from Canada, Europe, and the United States.
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| 18. |
- Puurula, Arto, et al.
(författare)
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Full-scale test to failure of a strengthened reinforced concrete bridge : calibration of assessment models for load-bearing capacities of existing bridges
- 2008
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Ingår i: Nordic Concrete Research. - 0800-6377. ; :2, s. 131-142
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Tidskriftsartikel (refereegranskat)abstract
- A reinforced concrete railway trough bridge has been strengthened and loaded to failure. The aim was to test and calibrate methods developed in the European Research Project "Sustainable Bridges" regarding: (a) condition appraisal and inspection, (b) load carrying capacity analysis, (c) monitoring and (d) strengthening of existing bridges. The tested methods proved to be useful and to give accurate predictions. A failure in combined shear, bending and torsion was reached for an applied mid span load of 11,7 MN. This was well predicted by enhanced methods but 20 to 50 % higher than ultimate load evaluated according to predictions based on common codes and models.
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| 19. |
- Puurula, Arto, et al.
(författare)
-
Test of a concrete bridge in Sweden : I. Assessment methods
- 2008
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Ingår i: Bridge Maintenance, Safety, Management, Health Monitoring and Informatics. - Boca Raton, Fla : Taylor and Francis Group. - 9780415468442 ; , s. 3385-3592
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Konferensbidrag (refereegranskat)
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| 20. |
- Sas, Gabriel, et al.
(författare)
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Tested versus code capacity of existing bridges : Three examples
- 2015
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Ingår i: IABSE Conference Geneva 2015. - Geneva : International Association for Bridge and Structural Engineering. - 9783857481406 ; , s. 727-734
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents the results from three tests to failure of different types of bridges: a two span reinforced concrete railway trough bridge; a five-span prestessed concrete beam bridge; and a one span metal railway truss bridge. The results show that the capacity of the structures are underestimated by current standards, while numerical analysis combined with material testing can provide more accurate results. Some examples are also presented on how deficiencies incapacity can be mitigated using fiber reinforced polymer strengthening systems.
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| 21. |
- Täljsten, Björn, 1961-, et al.
(författare)
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Assessment of prestressed concrete bridges - challenges
- 2020
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Ingår i: IABSE Symposium, Wroclaw 2020. - Zürich : International Association For Bridge And Structural Engineering (IABSE). ; , s. 487-494
-
Konferensbidrag (refereegranskat)abstract
- Prestressed concrete bridges are important parts of our infrastructure. They are susceptible to different kinds of deterioration processes. Examples of damages and deficiencies are cracking, corrosion, voids, bond loss, reduction of cover layer, delamination, fatigue and loss of stiffness and strength. This necessitates methods to continuously assess their condition in order to avoid problems that might lead to shorter service life or reduction of structural integrity. Many of the existing prestressed bridges in Europe are now approaching their design life length. However, with proper and continuous inspection, monitoring and assessment, we may plan proactive maintenance and the structural safety can be assured or – if necessary - increased. This will save both money and decrease the environmental impact of the structure.
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| 22. |
- Täljsten, Björn, 1961-, et al.
(författare)
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Prestressed Concrete Bridges - Condition Assessment and Future Challenges : A State-of-Art Report
- 2019
-
Rapport (refereegranskat)abstract
- Prestressed concrete bridges are susceptible to deterioration over time and it is vital to continually assess them in order to maintain their structural integrity and to prolong their service life. Important factors are corrosion of prestressing strands, wires and bars; remaining prestressing forces and concrete deterioration. In recent years, there has been an increased interest in monitoring and non-destructive testing to assess the state of bridges. It is essential to understand the behavior in ultimate and serviceability limit states and the level of safety, reliability and robustness. Calibration of Condition and Life Cycle Assessments are discussed by help of Full-Scale Tests of Bridges that are planned to be demolished. Repair and Strengthening methods are reviewed. Needs for Maintenance Strategies are outlined.
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| 23. |
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| 24. |
- Bagge, Niklas, 1987-, et al.
(författare)
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Assessment and failure test of a prestressed concrete bridge
- 2017
-
Ingår i: Life-Cycle of Engineering Systems. - Leiden : CRC Press/Balkema. - 9781138028470 ; , s. 1058-1063
-
Konferensbidrag (refereegranskat)abstract
- Tests have been carried out at service- and ultimate load levels of a 55 year-old prestressed concrete girder bridge. The bridge, located in Kiruna, Sweden, was continuous in five spans with a total length of 121.5 m. The overall aim of the study was to determinate the accuracy of assessment methods for existing structures and to provide procedures for optimized assessment. Before the tests a 2D finite element (FE) analysis was performed to predict the behavior and load-carrying capacity of the bridge. In order to more accurately assess the bridge response a 3D FE model has now been developed. The actual loading history and material properties has been considered in the model. A Life Cycle Cost Assessment of the bridge has also been performed
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| 25. |
- Bagge, Niklas, 1987-, et al.
(författare)
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Assessment of concrete bridges - Structural capacity : Experiences from full-scale testing to failure of a bridge in Kiruna
- 2017
-
Ingår i: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation. - Oslo : Nordic Concrete Federation. ; , s. 263-266
-
Konferensbidrag (refereegranskat)abstract
- To calibrate methods for condition assessment of prestressed concrete (PC) bridges, tests were carried out on a 55 year old five-span bridge with a length of 121 m in Kiruna in northern Sweden. Both non-destructive and destructive full-scale tests were performed. This paper presents results regarding methods for assessment of the structural capacity of concrete bridges.
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| 26. |
- Bagge, Niklas, et al.
(författare)
-
Full-Scale Test to Failure of a Prestressed Concrete Bridge in Kiruna
- 2014
-
Ingår i: Nordic Concrete Research. - 0800-6377. ; 50, s. 83-86
-
Tidskriftsartikel (refereegranskat)abstract
- To calibrate methods for condition assessment of prestressed concrete (PC) bridges, tests areplanned for a 50 year old five-span bridge with a length of 121 m in Kiruna in northern Sweden.Both non-destructive and destructive full-scale tests will be performed. This paper summarisesthe test programme, which comprises evaluation of the structural behaviour of the bridge, theresidual forces in the prestressed steel, methods for strengthening using carbon fibre reinforcedpolymers (CFRP) and the shear resistance of the bridge slab.
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| 27. |
- Bagge, Niklas, 1987-, et al.
(författare)
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Full-Scale Tests to Failure Compared to Assessments : Three Concrete Bridges
- 2018
-
Ingår i: High Tech Concrete. - Cham : Springer. - 9783319594705 - 9783319594712 ; , s. 1917-1924
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Konferensbidrag (refereegranskat)abstract
- Three Swedish concrete bridges have been tested to failure and the results have been compared to assessment using standard code models and advanced numerical methods.The three tested and assessed bridges were:(1)Lautajokk, a 29 year old one span (7 m) concrete trough bridge tested in fatigue to check the concrete shear capacity. (2)Ӧrnskldsvik, a 50 year old two span trough bridge (12 + 12 m) strengthened to avoid a bending failure. (3)Kiruna Mine Bridge, a 55 year old five span prestressed concrete road bridge (18 + 21 + 23 + 24 + 20 m) tested in shear and bending of the beams and punching of the slab. The main results in the paper are the experiences of the real failure types, the robustness/weakness of the bridges, and the accuracy of different codes and models. In all three cases the bridges had a considerable hidden capacity.
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| 28. |
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| 29. |
- Bagge, Niklas, 1987-
(författare)
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Structural assessment procedures for existing concrete bridges : Experiences from failure tests of the Kiruna Bridge
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Assessing existing bridges is an important task in the sustainable management ofinfrastructure. In practice, structural bridge assessments are usually conducted usingtraditional and standardised methods, despite knowledge that these methods oftenprovide conservative estimates. In addition, more advanced methods are available, suchas nonlinear finite element (FE) analysis, that are used for research purposes and cansimulate the structural behaviour of bridges more accurately. Therefore, it would beuseful to develop practical and reliable procedures for refined assessments using theseadvanced techniques.Focusing on the ultimate load-carrying capacity of existing concrete bridges, this thesispresents a procedure for structural assessments. The fundamental idea is to improve theassessment successively, as necessary to predict bridges’ structural behaviour adequately.The procedure involves a multi-level assessment strategy with four levels of structuralanalysis, and an integrated framework for safety verification. At the initial level (Level 1)of the multi-level strategy, traditional standardised methods are used, no failures arecovered implicitly in the structural analysis and action effects are verified using localresistances calculated using analytical models. In the subsequent enhanced levels (Levels2 – 4), nonlinear FE analysis is used for stepwise integration of the verification of flexural,shear-related and anchorage failures into the structural analysis. The framework for safetyverifications includes partial safety factor (PSF), global resistance safety factor (GRSF) andfull probabilistic methods. Within each of these groups, verifications of desired safetymargins can be conducted with varying degrees of complexity.To demonstrate and evaluate the proposed structural assessment procedure, comparativestudies have been carried out, based on full-scale tests of a prestressed concrete bridge.This was the Kiruna Bridge, located in the northernmost city in Sweden, which was duefor demolition as part of a city transformation project, necessitated by large grounddeformations caused by the large nearby mine. Thus, it was available for destructiveexperimental investigation within the doctoral project presented in this thesis. The bridgehad five continuous spans, was 121.5 m long and consisted of three parallel girders with a connecting slab at the top. Both the girders and slab were tested to failure to investigatetheir structural behaviour and load-carrying capacity. Non-destructive and destructivetests were also applied to determine the residual prestress forces in the bridge girders andinvestigate the in situ applicability of methods developed for this purpose. The so-calledsaw-cut method and decompression-load method were used after refinement to enabletheir application to structures of such complexity. The variation of the experimentallydetermined residual prestress forces was remarkably high, depending on the sectioninvestigated. There were also high degrees of uncertainty in estimated values, and thusare only regarded as indications of the residual prestress force.Level 1 analysis of the multi-level assessment strategy consistently underestimatedcapacity, relative to the test results, and did not provide accurate predictions of the shearrelatedfailure observed in the test. With linear FE analysis and local resistance modelsdefined by the European standard, Eurocode 2, the load-carrying capacity wasunderestimated by 32 % for the bridge girder and 55 % for the bridge deck slab. At theenhanced level of structural analysis (Level 3), nonlinear FE analyses predicted thecapacities with less than 2 % deviation from the test results and correctly predicted thefailure mode. However, for existing bridges there are many uncertainties, for instance,the FE simulations were sensitive to the level of residual prestressing, boundaryconditions and assumed material parameters. To accurately take these aspects intoaccount, bridge-specific information is crucial.The complete structural assessment procedure, combining the multi-level strategy andsafety verification framework, was evaluated in a case study. Experiences from theprevious comparative studies were used in an assessment of the Kiruna Bridge followingthe Swedish assessment code. The initial assessment at Level 1 of the multi-level strategyand safety verification, using the PSF method, indicated that the shear capacity of one ofthe girders was critical. The most adverse load case (a combination of permanent loads,prestressing and variable traffic loads) was further investigated through enhancedstructural analyses implicitly accounting for flexural and shear-related failures (Level 3).Nonlinear FE analysis and safety evaluation using the PSF method, several variants of theGRSF method and the full probabilistic analysis for resistance indicated that the permittedaxle load for the critical classification vehicle could be 5.6 – 6.5 times higher than thelimit obtained from the initial assessment at Level 1. However, the study also indicatedthat the model uncertainty was not fully considered in these values. The modeluncertainty was shown to have strong effects on the safety verification and (thus)permissible axle loads. The case study also highlighted the need for a strategy forsuccessively improving structural analysis to improve understanding of bridges’ structuralbehaviour. The refined analysis indicated a complex failure mode, with yielding of thestirrups in the bridge girders and transverse flexural reinforcement in the bridge deck slab,but with a final shear failure of the slab. It would be impossible to capture suchcomplexity in a traditional standardised assessment, which (as mentioned) indicated thatthe shear capacity of the girder limited permissible axle loads. However, nonlinear FEanalyses are computationally demanding, and numerous modelling choices are required.Besides a strategy for rationally improving the analysis and helping analysts to focus oncritical aspects, detailed guidelines for nonlinear FE analysis should be applied to reduce the analyst-dependent variability of results and (thus) the model uncertainty. Clearly, toensure the validity of bridge assessment methods under in situ conditions, theirevaluations should include in situ tests. This thesis presents outcomes of such tests, therebyhighlighting important aspects for future improvements in the assessment of existingbridges.
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| 30. |
- Bell, Brian, et al.
(författare)
-
Sustainable Bridges - Past and Future Reflections on a European Project 2003-2007
- 2023
-
Ingår i: IABSE Congress, New Delhi 2023: Engineering for Sustainable Development, Report. ; , s. 690-698
-
Konferensbidrag (refereegranskat)abstract
- Twenty years ago, in 2003, a European project was started to increase the sustainability of existing railway bridges. This paper summarises what was achieved and looks ahead. Nine Working Packages were organized: (1) Background material; (2) Guidance by stakeholders; (3) Condition Assessment and Inspection Guidelines; (4) Loads, Capacity and Resistance Guidelines; (5) Monitoring Guidelines; (6) Repair and Strengthening Guidelines; (7) Demonstration with Field testing of Bridges; (8) Demonstration on Monitoring on Bridges; and (9) Training and Dissemination Some of the main results (from 4 Guidelines and 47 Background documents) are highlighted and some experiences, conclusions and thoughts about the future are given. Hidden strengths and weaknesses are discussed, analyses and codes for assessment can be improved, new monitoring and strengthening methods are available and life length can be prolonged.
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| 31. |
- Bennitz, Anders, et al.
(författare)
-
CFRP strengthening of a railway concrete trough bridge : a case study
- 2012
-
Ingår i: Structure and Infrastructure Engineering. - : Informa UK Limited. - 1573-2479 .- 1744-8980. ; 8:9, s. 801-816
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an upgrading and monitoring of a Swedish concrete railway bridge. The methods used for the upgrading as well as for the monitoring are innovative and new. Carbon fibre tubes are inserted in holes in the bridge deck, drilled in the transverse direction of the slab at a location ca. 40 mm from the top. Carbon fibre NSMR bars are bonded in transverse grooves in the soffit of the slab. Both methods are intended to increase the transverse bending moment capacity of the troughs' bottom slab in the ultimate limit state. Monitoring is performed to verify the effectiveness of the strengthening and to understand the behaviour of the bridge. However, for obvious reasons, monitoring is only carried out in the SLS (service limit state). Even though only marginal effects of strengthening could be recorded in the SLS, both the strengthening and monitoring were considered successful at a cost of approximately 8% of the total cost of a new bridge replacement.
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| 32. |
- Bennitz, Anders, et al.
(författare)
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External prestressing of RC T-beams with CFRP tendons
- 2009
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Ingår i: Proceedings of the 9th International Symposium on Fiber-Reinforced Polymer Reinforcement for Concrete Structures. - Adeleide : University of Adelaide. - 9780980675504
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Konferensbidrag (refereegranskat)
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| 33. |
- Bennitz, Anders, et al.
(författare)
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Failure modes of prestressed CFRP rods in a wedge anchored set-up
- 2009
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Ingår i: Advanced Composites in Construction (ACIC) 2009 Conference Proceedings. - : ACIC. ; , s. 104-114
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Konferensbidrag (refereegranskat)abstract
- In the process of developing a new wedge anchorage to anchor prestressed CFRP rods, five different anchorage designs were manufactured. These designs have led to a constantly increased ultimate failure load of the prestressing system and an eventual load level above 95% of the ultimate failure load of the rod was achieved. If 100% efficiency is achieved the anchorage does not reduce the capacity of the system, but failure is then governed by the capacity of the rod itself, which is considered favourable and required by several guidelines. In the process seven different failure modes were identified: soft slip, power slip, cutting of fibres, crushing of rod, bending of fibres, frontal overload and intermediate rupture. In this paper the failure modes are discussed further. The failures are documented with explanatory figures and their backgrounds are found in the theory. Suggestions are given on how these failures can be avoided in theory and practice. From the experiences gained in the project, it is concluded that it is a challenging task to create a fully mechanical anchorage for CFRP tendons and that the failure margins are small between a successful and an unsuccesful anchorage system.
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| 34. |
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| 35. |
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| 36. |
- Bennitz, Anders, et al.
(författare)
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Reinforced concrete T-beams externally prestressed with unbonded carbon fiber-reinforced polymer tendons
- 2012
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Ingår i: ACI Structural Journal. - : American Concrete Institute. - 0889-3241 .- 1944-7361. ; 109:4, s. 521-530
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Tidskriftsartikel (refereegranskat)abstract
- This study describes a series of experiments examining the behavior of seven beams prestressed with unbonded external carbon fiber-reinforced polymer (CFRP) tendons anchored using a newly developed anchorage and post-tensioning system. The effects of varying the initial tendon depth, prestressing force, and the presence of a deviator were investigated. The results were compared to those observed with analogous beams prestressed with steel tendons, common beam theory, and predictions made using an analytical model adapted from the literature. It was found that steel and CFRP tendons had very similar effects on the structural behavior of the strengthened beams; the minor differences that were observed are attributed to the difference between the modulus of elasticity of the CFRP and the steel used in the tests. The models predicted the beams’ load-bearing behavior accurately but were less effective at predicting the stress experienced by the tendons.
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| 37. |
- Bennitz, Anders, et al.
(författare)
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Strengthening of a railway bridge with NSMR and CFRP tubes
- 2008
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Ingår i: FRP Composites in Civil Engineering. - Dübendorf : EMPA-Akademie. - 9783905594508
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Konferensbidrag (refereegranskat)abstract
- Strengthening of structures with CFRP is considered today as an accepted method in the upgrading of concrete structures. This paper presents the use of two different CFRP strengthening systems combined to extend the service life of a Swedish double-trough-doubletrack railway bridge, constructed in concrete with a 10 meter span. One system is the reliable NSMR (Near Surface Mounted Reinforcement) while the other is new. They were used with the intention to strengthen the interior of a concrete structure using integrated CFRP tubes. Both systems were used to increase the tensile flexural strength of the slab transverse to the tracks. NSMR bars were positioned in the bottom concrete cover of the trough's bottom-slabs, while the new system was inserted in holes drilled through the bridge in the cross direction and located in the upper part of the slab. In connection with the strengthening monitoring was conducted in order to obtain an understanding of the bridge behaviour before and after strengthening, and to demonstrate any effects of the extra CFRP reinforcement. Results from these measurements are presented together with how the strengthening work was carried out. Sensors on bars and tubes show evidence of utilization of the CFRP while displacement sensors and strain gauges on the steel reinforcement show minor effect due to the small loads in the service limit state.
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| 38. |
- Bennitz, Anders, et al.
(författare)
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Undersökning av skjuvförband i trä : provning av bulttyper för Vasaskeppet
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Föreliggande rapport är resultatet av laboratorieförsök vilka utförts på avdelningen för byggkonstruktion vid Luleå tekniska universitet. Försöken har genomförts under slutet av 2007 och är en direkt fortsättning av tidigare försök från 2004 och 2005. De tidigare rapporterna pekade på ett behov av fortsatt provning. Föreliggande rapport är således en fortsättning av tidigare arbete, dock med vidareutveckling av möjliga bulltyper för Vasaskeppet. De testade bulltyperna har konstruerats och tillverkats i Statens Maritima Museer regi av Anders Ahlgren. Försöken har genomförts vid Luleå tekniska universitet och Complab, av Civ. Ing. Georg Danielsson samt forskarstuderande Anders Bennitz.
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| 39. |
- Bergström, Markus, et al.
(författare)
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Bro över Järpströmmen : kompletterande mätning av påkänningar vid tung överfart
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Kompletterande mätning på bron över Järpströmmen genomfördes då lasten vid föregående mätning ansågs för liten. Vid aktuell mätning bestod lasten av ett transportekipage med en totalvikt på cirka 400 ton fördelat på 20 hjulaxlar och en bit över 100 däck. Mycket låg påkänning i kolfibermaterial och stålarmering, i storleksordningen omkring 5 m/m. Den låga påkänningen härleds inte till en för låg last, då ekipagets tyngd är stor. Däremot kan mätresultaten förklaras i att tvärkraftsarmeringen och förstärkningen inte tar last förrän uppsprickning av brobetongen inträffar. Betongbrons spricklast förutsätts inte vara uppnådd vid aktuell lastnivå, vilket förklarar de små töjningarna på armering och kolfiber. Detta resonemang baseras på genomförda försök (Carolin, 2003). Erfarenhetsmässigt är tvärkraftsförstärkning med kolfiberlaminat en fungerande och effektiv metod för att uppgradera en konstruktion. Kolfiberförstärkningen har konsekvent en töjning omkring 5 με vid överfart, vilket visar att förstärkningen tar last och därmed fungerar. Ingen tendens av vidhäftningsproblem finns vid aktuell lastnivå, vilket stöds av att armeringen och kolfibermaterialet töjs lika mycket. Detta betyder att förstärkningen fortsätter ta mer last vid ökad belastning. Förstärkningen kan därför förutsättas bidra till en ökad kapacitet i brottgränstillstånd, då uppsprickning av betong inträffar, trots att effekterna är svåra att bestyrka i bruksgränstillstånd och utförd mätning.
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| 40. |
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| 41. |
- Bergström, Markus, et al.
(författare)
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Degradation of structural performance : Experiment introduction and expected results
- 2006
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Ingår i: Bridge maintenance, safety, management, life-cycle performance and cost. - London : Taylor & Francis Group. - 0415403154 - 9780415403153 ; , s. 251-252
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Much effort has been put on investigating degradation of concrete structures, repair and upgrading separately, as can be read in numerous publications, i.e., Green et. al. (2003), Morgan (1995) and Täljsten (2004). However, an overall view has not been taken where the whole life cycle of a concrete structure is considered. In particular, no laboratory tests have been presented in the literature to the author's knowledge. A structure passes several stages during its life. Normally two major stages are discerned, the service limit state (SLS) and the ultimate limit state (ULS). Concrete structures are designed for both these stages. In the SLS normally the deformation and crack widths are controlled. Deformation due to comfort demands and crack widths due to durability demands. In the ULS the structure is designed for its ultimate capacity - which for civil and building structures almost never is reached. From a safety aspect the ULS is most important; however, for the client the SLS with regard to maintenance, repair and upgrading are most costly. If the SLS was better understood, in particular from a rehabilitation point of view, more robust and cost effective repair and upgrading system could be developed. (Figure Presented). This paper is also a part of "Sustainable bridges". "Sustainable bridges" is a European project which focus is to preserve bridges throughout Europe and create unanimous codes for all participating countries. The project presented in this paper, Degradation of Structural Performance (DOSP), will investigate the behaviour of concrete beams which will endure a simulated life cycle procedure. The test program will direct the beams from full strength of the intact beam through degradation, repair and upgrading with FRP plate bonding to its original strength again or near. The cross-sectional strain distribution will be monitored during the test using Fibre Bragg Grating (FBG) Strain Sensors as well as traditional strain gauges. This gives the possibility of comparing results in between the two monitoring techniques over proportionately long time span. An accelerated corrosion procedure is used to corrode the flexural tensile reinforcement. The cycle may be divided into seven stages, a to g, presented shortly in Figure 1, Horrigmoe (1998) and Sand 2001. This life cycle is possible in the real case scenario for bridges or other concrete structures which are subjected to chlorides, i.e. de-icing salt or sea water
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| 42. |
- Bergström, Markus, et al.
(författare)
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Failure load test of a CFRP strengthened railway bridge in Örnsköldsvik, Sweden
- 2009
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Ingår i: Journal of Bridge Engineering. - 1084-0702 .- 1943-5592. ; 14:5, s. 300-308
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Tidskriftsartikel (refereegranskat)abstract
- The results obtained when performing a load test to failure of an existing structure are valuable when assessing calculation models, updating finite element models, and investigating the true structural behavior. In this paper a destructive testing and monitoring of a railway bridge in Örnsköldsvik, Sweden is presented. In this particular test the shear capacity of the concrete girders was of primary interest. However, for any reasonable placement of the load (a line load placed transverse to the track direction) a bending failure would occur. This problem was solved by strengthening for flexure using carbon fiber reinforced polymer (CFRP) rectangular rods epoxy bonded in sawed up slots, e.g., near surface mounted reinforcement. The strengthening was very successful and resulted in a desired shear failure when the bridge was loaded to failure. The load-carrying capacity in bending for the unstrengthened and strengthened bridge as well as the shear capacity was predicted with Monte Carlo simulations. The particular calculation presented showed that there was a 25% probability of a bending failure instead of a shear failure. Monitoring showed that the strengthening reduced the strain in the tensile steel reinforcement by approximately 10%, and increased the height of the compressed zone by 100 mm. When the shear failure occurred, the utilization of the compression concrete and CFRP rods were 100 and 87.5%, respectively. This indicates that a bending failure indeed was about to occur, even though the final failure was in shear.
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| 43. |
- Bergström, Markus, et al.
(författare)
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Reparation och förstärkning av betongkonstruktioner
- 2007
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Ingår i: Bygg och Teknik. - 0281-658X .- 2002-8350. ; 99:7, s. 48-50
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Att utnyttja moderna metoder och material för att återställa befintliga och åldrande betongkonstruktioner till ett funktionellt skick är viktigt. Studier kring möjligheter att öka såväl den ekonomiska som fysiska livslängden är ett omfattande forskningsområde. Även de praktiska tillämpningarna ökar i antal. Trots att erfarenheten och kunskapen att bygga långsiktigt hållbara betongkonstruktioner hela tiden ökar finns det relativt nya konstruktioner som inte uppfyller ställda krav på säkerhet och funktion. Det finns dessutom otaliga betongkonstruktioner som har brukats under flera årtionden som börjar visa tecken på omfattande brister.
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| 44. |
- Bergström, Markus, et al.
(författare)
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Structural health monitoring of degrading concrete beams in a laboratory environment
- 2006
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Ingår i: Composites in Civil Engineering. - : International Institute for FRP in Construction (IIFC). ; , s. 335-338
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Much effort has been invested separately on degradation, repair and upgrading of concrete structures. However, few holistic studies including laboratory testing have been performed on the entire cycle during a structures life. Reinforced concrete is the most widely used building material in the world. Normally the life of concrete structures is very long. However, concrete structures possess one drawback; at least in severe environments, the steel reinforcement may corrode. The effects can clearly be seen when the steel reinforcement is attacked by chlorides. The reduced steel cross-section area and loss of bond strength between steel and concrete will lead to increased deformations, cracking and premature ultimate load, thus affecting both the serviceability limit state (SLS) and the ultimate limit state (ULS). Procedures to repair and upgrade the damaged structure are used to increase the structural performance. They follow the structural member of time, a SHM (Structural Health Monitoring) approach is adapted to this project. By applying SHM to a degrading structure it assures that it will keep up to current standards by continuous monitoring, analysing, evaluation and eventually also retrofitting.
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| 45. |
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| 46. |
- Blanksvärd, Thomas, et al.
(författare)
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Mineral based bonding of CFRP to strengthen concrete structures
- 2006
-
Ingår i: Bridge maintenance, safety, management, life-cycle performance and cost. - London : Taylor & Francis Group. - 0415403154 - 9780415403153 ; , s. 1057-1058
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Strengthening of concrete structures with epoxy bonded carbon fiber reinforced polymers (CFRP) has been proved to be a good strengthening technique. However, this strengthening technique with epoxy adhesives do contain some disadvantages such as diffusion closeness, thermal incompatibility to the base concrete, working environment and minimum application temperature. Some of these drawbacks can be overcome by substituting the epoxy to a polymer reinforced mortar as the bonding agent. This work presents a pilot study with CFRP strengthened concrete beams. In this case the epoxy bonded CFRP has been replaced with a mineral based composite (MBC). The results from the pilot study indicates that the MBC strengthening system do achieve very good composite action and strengthening effects. These results warrant for further research and improvement of the MBC strengthening system
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| 47. |
- Blanksvärd, Thomas, et al.
(författare)
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Mineral based bonding to strengthen concrete structures
- 2006
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Ingår i: Advances in bridge maintenance, safety, management and life-cycle performance. - London : Taylor and Francis Group. - 9780415403153
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Konferensbidrag (refereegranskat)
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| 48. |
- Blanksvärd, Thomas, et al.
(författare)
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Mineral based strengthening systems for upgrading RC Structures
- 2012
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Ingår i: Fib symposium Stockholm 2012. - Stockholm : Swedish Conrete Association. - 9789198009811 ; , s. 363-366
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Konferensbidrag (refereegranskat)abstract
- During the last two decades, strengthening concrete structures with epoxy bonded carbon fibre reinforced polymers (CFRP) have shown excellent results in increasing bearing capacity. However, there are some limitations with epoxy coated concrete surfaces, e.g.; low permeability which may provoke freeze/thaw problems, poor thermal compatibility to the concrete substrate which makes epoxy coating more sensitive to the surrounding temperature and regulations when it comes to the safety and health (allergic reactions) of applicators and third party users. In this respect, using mineral based composites (MBC) may overcome some of these challenges associated with epoxy bonded strengthening systems. MBC, in this context, refers to high strength fibres bonded to the surface using a mineral based bonding agent. This study is examining the cracking behaviour and strain development of shear MBC strengthened RC beams. The results show that using MBC as shear strengthening postpones the formation of macro-cracks and that a considerable strengthening effect is achieved by using MBC.
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| 49. |
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| 50. |
- Blanksvärd, Thomas, et al.
(författare)
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Shear strengthening of concrete structures with the use of mineral-based composites
- 2009
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Ingår i: Journal of composites for construction. - 1090-0268 .- 1943-5614. ; 13:1, s. 25-34
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Tidskriftsartikel (refereegranskat)abstract
- Rehabilitation and strengthening of concrete structures have become more common during the last 10-15 years, partly due to a large stock of old structures and partly due to concrete deterioration. Also factors such as lack of understanding and the consequences of chloride attack affect the need for rehabilitation. In addition, more traffic and heavier loads lead to the need for upgrading. Existing externally bonded strengthening systems using fiber-reinforced polymers (FRP) and epoxy as bonding agents have been proven to be a good approach to repair and strengthen concrete structures. However, the use of epoxy bonding agents has some disadvantages in the form of incompatibilities with the base concrete. It is, therefore, of interest to substitute epoxy with systems that have better compatibility properties with the base concrete, for example, cementitious bonding agents. This paper presents a study on reinforced concrete beams strengthened in shear with the use of cementitious bonding agents and carbon fiber grids, denoted as mineral-based composites (MBC). In this study it is shown that the MBC system has a strengthening effect corresponding to that of strengthening systems using epoxy bonding agents and carbon fiber sheets. Different designs and material properties of the MBC system have been tested. An extensive monitoring setup has been carried out using traditional strain gauges and photometric strain measurements to obtain strains in steel reinforcement, in FRP, and strain fields on the strengthened surface. It has been shown that the use of MBC reduces strains in the steel stirrups and surface cracks even for low load steps as compared to a nonstrengthened concrete beam.
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