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  • 1.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bernspång, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Trafikverket.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Full-Scale Test to Failure of a Prestressed Concrete Bridge in Kiruna2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 83-86Article in journal (Refereed)
    Abstract [en]

    To calibrate methods for condition assessment of prestressed concrete (PC) bridges, tests are planned 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 summarises the test programme, which comprises evaluation of the structural behaviour of the bridge, the residual forces in the prestressed steel, methods for strengthening using carbon fibre reinforced polymers (CFRP) and the shear resistance of the bridge slab.

  • 2.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bernspång, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Norut Northern Research Institute, Narvik.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. College of Civil Engineering, Southeast University, Nanjing.
    Carolin, Anders
    Trafikverket, Trafikverket, Luleå.
    Performance of a prestressed concrete bridge loaded to failure2015In: IABSE Conference Geneva 2015: Structural Engineering: Providing Solutions to Global Challenges, Geneva: International Association for Bridge and Structural Engineering, 2015, p. 1088-1095Conference paper (Other academic)
  • 3.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Instrumentation and Full-Scale Test of a Post-Tensioned Concrete Bridge2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 51, p. 63-83Article in journal (Refereed)
    Abstract [en]

    To meet new demands, existing bridges might be in need for repair, upgrading or replacement. To assist such efforts a 55-year-old post-tensioned concrete bridge has been comprehensively tested to calibrate methods for assessing bridges more robustly. The programme included strengthening, with two systems based on carbon fibre reinforced polymers (CFRPs), failure loading of the bridge’s girders and slab, and determination of post-tension cables’ condition and the material behaviour. The complete test programme and related instrumentation are summarised, and some general results are presented. The measurements address several current uncertainties, thereby providing foundations for both assessing existing bridges’ condition more accurately and future research.

  • 4.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sundquist, Håkan
    Royal Institute of Technology.
    Carolin, Anders
    Trafikverket, Luleå.
    Assessment and failure test of a prestressed concrete bridge2017In: Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure / [ed] Jaap Bakker; Dan M Frangopol; Klaas van Breugel, Leiden: CRC Press/Balkema , 2017, p. 1058-1063Conference paper (Refereed)
    Abstract [en]

    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

  • 5.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Puurula, Arto
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Carolin, Anders
    Trafikverket, Luleå.
    Full-Scale Tests to Failure Compared to Assessments: Three Concrete Bridges2017In: High Tech Concrete: Where Technology and Engineering Meet - Proceedings of the 2017 fib Symposium / [ed] Lukovic M.,Hordijk D.A., Cham: Springer, 2017, p. 1917-1924Conference paper (Refereed)
    Abstract [en]

    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. (1)

      Lautajokk, a 29 year old one span (7 m) concrete trough bridge tested in fatigue to check the concrete shear capacity.

       
    2. (2)

      Ӧrnskldsvik, a 50 year old two span trough bridge (12 + 12 m) strengthened to avoid a bending failure.

       
    3. (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.

  • 6.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. WSP, Luleå, Sweden.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Norut Teknik, Norut, Norge.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Bernspång, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Carolin, Anders
    Trafikverket, Luleå.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Assessment of concrete bridges - Structural capacity: Experiences from full-scale testing to failure of a bridge in Kiruna2017In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation, Oslo: Nordic Concrete Federation , 2017, p. 263-266Conference paper (Refereed)
    Abstract [en]

    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.

  • 7.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Tu, Yongming
    College of Civil Engineering, Southeast University, Nanjing.
    Carolin, Anders
    Trafikverket.
    Loading to failure of a 55 year old prestressed concrete bridge2015In: IABSE Workshop Helsinki 2015: Safety, Robustness and Condition Assessments of Structures, Zurich: International Association for Bridge and Structural Engineering, 2015, p. 130-137Conference paper (Refereed)
    Abstract [en]

    In order to provide relevant data for calibration and development of methods for assessment ofexisting bridges, a 55 year old posttensioned concrete bridge has been subjected to non-destructiveand destructive tests. The bridge, located in Kiruna, Sweden, was a 121 m long girder bridgecontinuous in five spans. The test programme included failure loading of the girders and slab,respectively, condition assessment of the post-tensioned cables and material tests. Moreover, twostrengthening systems, using carbon fibre reinforcing polymer (CFRP), were evaluated. In this paperthe experimental programme and some preliminary results are presented to give an insight to researchproject.

  • 8.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. WSP, Luleå, Sweden.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Norut Teknik, Norut, Norge.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Carolin, Anders
    Trafikverket, Luleå.
    Paulsson, Björn
    Trafikverket; UIC, Paris, France; Charmec, Chalmers tekn högskola.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Assessment of concrete bridges - Prestress forces: Experiences from full-scale testing to failure of a bridge in Kiruna2017In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation, Oslo: Nordic Concrete Federation , 2017, p. 267-270Conference paper (Refereed)
    Abstract [en]

    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.

  • 9.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Förstärkning av betong med mineralbaserade kompositer2007In: V-byggaren : väg- och vattenbyggaren, ISSN 0283-5363, no 5, p. 70-75Article in journal (Other academic)
  • 10.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Mechanical properties of different geometries of CFRP grid: tensile evaluation of material properties2006Report (Other academic)
    Abstract [en]

    There are a number of components included in strengthening of concrete with mineral based composites; base concrete that is in need of strengthening, primers, polymer modified cement bonding agents and carbon fibre reinforced polymers (CFRP). CFRP are light weight composites of carbon fibres imbedded in a matrix that can be tailor-made into different geometries. This report is a part of an ongoing evaluation of a concrete strengthening technique using mineral based composites. This report was done to evaluate the tensile properties of different CFRP grids included in strengthening of concrete with mineral based composites. The experimental test set-up was performed as pure tensile of smaller parts of the different grids. The main mechanical properties presented in the report are failure stress, modulus of elasticity and failure strain. The result was compared to the values provided by the manufacturer. In the results no clear trends was evident between the experimental values and the manufacturer values. In the results it can be concluded that the mechanical properties provided by the manufacturer can not be used as design values. The experimental values were both higher and lower than the manufacturer values for the failure stress and modulus of elasticity. Different failure types of the grids are illustrated in the report.

  • 11.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Mätprogram för broarna över Åby älv och Rautasjokk: FAS 22013Report (Other academic)
  • 12.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Mätprogram för broarna över Åby älv och Rautasjokk: Utmattning och överlast2012Report (Other academic)
    Abstract [sv]

    Den här rapporten är beställd av trafikverket som en förstudie om förslag till möjligheterna att mäta på en bro över Åby älv som ligger på stambanan, samt vilka resultat som detta skulle kunna medföra.

  • 13.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Strengthening of concrete structures by the use of mineral based composites2007Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Strengthening of concrete structures with epoxy bonded carbon fiber reinforced polymers (CFRP) has been proved to be an excellent strengthening technique. However, using epoxy adhesives for bonding do contain some disadvantages such as diffusion closeness, thermal incompatibility to the base concrete, regulations regarding the working environment and minimum application temperature. Some of these drawbacks can be lessened by substituting the epoxy to a polymer reinforced mortar as the bonding agent. A new acronym for strengthening concrete structures with CFRP and polymer reinforced mortars is introduced, mineral based composites (MBC). This thesis presents experimental tests for both flexural strengthening and shear strengthening techniques using CFRP grids and polymer modified mortar as the bonding agent are presented. Flexural strengthening using the MBC system was designed as a pilot study to evaluate suitability of different mortars with different mechanical properties. The outcome of the pilot study on flexural strengthened small scale concrete beams gave indications on the choice of mortar used in the MBC system. A total amount of 21 concrete beams with and without shear strengthening subjected to four-point bending is evaluated in the thesis. The concrete beams were 4.5 m long and had a rectangular cross section of 180 x 500 mm. A number of parameters were varied for these beam specimens namely; concrete strength, shear reinforcement design, mortar properties, grid design and the addition of flexural strengthening using Near Surface Mounted Reinforcement (NSMR). Considering the steel shear reinforcement, three different variations were utilized; no shear reinforcement, a stirrup distance of 250 mm and 350 mm respectively. The results from the experimental study of the shear capacity using MBC on beams with no shear reinforcement indicates that strengthening concrete structures with the MBC system has competitive properties compared to epoxy bonded strengthening techniques. The MBC system reached 97% of the ultimate load achieved by a strengthening system with vertically applied epoxy bonded carbon fibre sheets. The ultimate failure load was increased with the increase of carbon fibre amount in the grid. Using a grid with small distance between the CFRP tows generated a higher first visible shear crack load. A simplified analytical design proposal to estimate the shear resistance contribution of the MBC strengthening system is proposed in the thesis. Reasonable results were obtained compared to experimental ultimate failure loads. Strains were monitored in the longitudinal steel reinforcement and the steel stirrups for the beams with internal steel shear reinforcement. Here it as clear that the use of the MBC strengthening system reduces the strains in the steel stirrups. Further, photmetric strain measurement on the surface of the strengthening system was also assessed. The use of the MBC strengthening system also reduces the prinicpal strain at the surface of the shear strengthening system. It can be concluded that the MBC strengthening system has great potentials to strengthen concrete structures. Further research are however needed in both development of the materials included

  • 14.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Strengthening of concrete structures by the use of mineral based composites: system and design models for flexure and shear2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A great number of society's resources are invested in existing concrete structures, such as bridges, tunnels, different kind of buildings etc. All of these structures have both an expected function and an expected life span. However, both the function and the life span can be influenced by external factors, e.g. degradation and altered load situations. Further influencing aspects could be mistakes in design or during the construction phase. Repairing and/or strengthening these structures could maintain or increase the function as well as the life span.To strengthen concrete structures by using adhesively bonded fibres or fibre reinforced polymers (FRP) has been shown to be an excellent way of improving the load bearing capacity. The most common adhesive used for this type of strengthening is epoxies. Unfortunately, there are some drawbacks with the use of epoxy adhesives such as diffusion tightness, poor thermal compatibility with concrete and requirements for a safe working environment which might lead to allergic reactions if proper protective clothing is not used. A further limiting factor is the requirement on the surrounding temperature at application. A commonly recommended minimum temperature at the time for application is 10°C, which makes the preparations regarding application during colder seasons much more complicated. However, some of these drawbacks could be reduced by substituting the epoxy adhesive for a mineral-based bonding agent with similar material properties as concrete.The strengthening system and also the topic of this thesis is termed "mineral-based composites" (MBC). The MBC consists in this context of grids of carbon FRP with high tensile strength that are bonded to an existing concrete surface by the use of a cement based bonding agent.The scientific approach in this thesis includes analytical methods to describe load bearing capacity for the strengthened concrete structure in both flexure and shear. The analytical approaches are then verified against experimental results. Above the theoretical and experimental performance of the MBC system a review of state of the art research has been made in order to collate and map existing mineral-based strengthening systems other than the MBC system.To develop and verify the theoretical models and to compare the performance of the MBC system to other possible designs of mineral-based strengthening systems, six papers are appended in the thesis. - The first paper describes the performance of the MBC system when used in flexural strengthening. The experimental program in this paper consists of a concrete slab strengthened with both the MBC system and epoxy based system. In addition, a parametric study was made on small scale beam specimens to evaluate the performance of using different cement-based bonding agents.- The second paper describes the performance of the MBC system when used as shear strengthening. This study consists of experimental results of 23 reinforced concrete beams with different concrete qualities, internal shear reinforcement ratios together with different variations of the CFRP grid design and mineralbased bonding agents. In addition, a comparison is also made to traditional epoxy-based strengthening. This paper also has an analytical approach to estimate the shear resistance.- The third paper describes existing mineral-based strengthening systems and how these perform in comparison to the proposed MBC strengthening system in shear and flexure.- The fourth paper maps different possibilities to design and combine various materials in order to obtain a mineral-based strengthening system. This paper also consists of experimental research on the tensile behaviour of the MBC system when using high performance fibre reinforced cementitious bonding agents (engineered cementitious composites - ECC). In addition, these results and discussions are also coupled to the observations made in flexural and shear strengthening.- The fifth paper gives suggestions on how to estimate the shear bearing capacity of MBC strengthened concrete beams. The suggested shear design approaches are mainly based on traditional shear design models based on truss analogy, but one design presented is based on the compression field theory.- The sixth and last paper describes the strain development in a shear strengthened concrete beam both with and without the MBC system. All of the results from the investigations made in this thesis indicate that the MBC system contributes to increasing the load bearing capacity for strengthened concrete structures considerably. It is also shown that the MBC system can give competitive strengthening effects compared to existing epoxy bonded strengthening systems. From the experimental investigations on the shear strengthened beams it is shown that the strains in the shear span are lowered compared to a non strengthened specimen. This reduction of strains is also shown in the transition zone between the development of macro cracks from micro cracks. The suggested analytical approach in order to estimate the load bearing capacity of strengthened concrete structures in both flexure and shear indicates that realistic estimations can be made. The flexural design is straightforward while the shear design is more intricate. It is however concluded that a simple and safe design could be made based on the "additional" approach using a 45° truss.

  • 15. Blanksvärd, Thomas
    et al.
    Carolin, Anders
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Rosell, E.
    Swedish Road Administration, Borlänge.
    Mineral based bonding of CFRP to strengthen concrete structures2006In: Bridge maintenance, safety, management, life-cycle performance and cost: proceedings of the Third International Conference on Bridge Maintenance, Safety and Management, Porto, Portugal, 16 - 19 July 2006 / [ed] Paulo J. S. Cruz; Dan M. Frangopol, London: Taylor & Francis Group, 2006, p. 1057-1058Conference paper (Other academic)
    Abstract [en]

    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

  • 16. Blanksvärd, Thomas
    et al.
    Carolin, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Rosell, Ebbe
    Mineral based bonding to strengthen concrete structures2006In: Advances in bridge maintenance, safety, management and life-cycle performance: Proceedings of the Third International Conference on Bridge Maintenance, Safety and Management, IABMAS 06, London: Taylor and Francis Group , 2006Conference paper (Refereed)
  • 17.
    Blanksvärd, Thomas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Häggström, Jens
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Paulsson, Björn
    UIC, Trafikverket.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Test to failure of a steel truss bridge: Calibration of assessment methods2014In: Bridge Maintenance, Safety, Management and Life Extension: proceedings of the Seventh International Conference of Bridge Maintenance, Safety and Management, 7-11 July 2014, Shanghai, China / [ed] Airong Chen; Dan M. Frangopol; Xin Ruan, London: CRC Press, Taylor & Francis Group , 2014, p. 1076-1081Conference paper (Refereed)
    Abstract [en]

    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.

  • 18. Blanksvärd, Thomas
    et al.
    Malaga, Katarina
    Swedish Concrete Institute (CBI).
    Örjan, Petersson
    Strängbetong.
    Tammo, Kristian
    Swedish Concrete Institute (CBI).
    Flansbjer, Mattias
    Statens Provningsanstallt (SP).
    Textile reinforced concrete sandwich panels2011In: Nordic Concrete Research: Proceedings of the XXI Nordic Concrete Symposium, Hämeenlinna, Finland 2011, Oslo: Norsk Betongforening , 2011, p. 517-520Conference paper (Refereed)
  • 19.
    Blanksvärd, Thomas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Strengthening Concrete Structures using Mineral Based Composites2013In: Proceedings of the 11th International Symposium on Fiber Reinforced Polymer for Reinforced Concrete Structures / [ed] Joaquim Barros; José Sena-Cruz, Universidade do Minho , 2013Conference paper (Refereed)
    Abstract [en]

    During the last two decades, strengthening concrete structures with epoxy bonded carbon fiber reinforced polymers (CFRP) has 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 security 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 fibers bonded to the surface using a mineral based bonding agent. This study examines the cracking behavior 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.

  • 20. Blanksvärd, Thomas
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    CFRP and mineral based bonding agents to strengthen concrete structures2008In: Proceedings, Nordic Concrete Research, Bålsta, Sweden: [ ... XXth Symposium on Nordic Concrete Research & Development ... The current proceedings contain 90 summaries of oral poster presentations] / [ed] Johan Silfwerbrand, Oslo: Norsk Betongforening , 2008, p. 90-91Conference paper (Refereed)
  • 21. Blanksvärd, Thomas
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Strengthening of concrete structures with cement based bonded composites2008In: Nordic Concrete Research, ISSN 0800-6377, no 2, p. 143-163Article in journal (Refereed)
  • 22.
    Blanksvärd, Thomas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Using mineral based composites for shear strengthening concrete members2012In: Concrete solutions: proceedings of Concrete solutions, 4th International Conference on Concrete Repair, Dresden, Germany, 26 - 28 September 2011 / [ed] Michael Grantham; Viktor Mechtcherine, Boca Raton, Fla.: CRC Press/Balkema , 2012, p. 623-629Conference paper (Refereed)
    Abstract [en]

    During the last two decades, strengthening concrete structures with epoxy bonded carbon fiber reinforced polymers (CFRP) has 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 security 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 fibers bonded to the surface using a mineral based bonding agent. This study examines the cracking behavior 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

  • 23. Blanksvärd, Thomas
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Shear crack propagation in MBC strengthened concrete beams2008In: FRP Composites in Civil Engineering: proceedings of the 4th International Conference on FRP Composites in Civil Engineering ; Zurich, Switzerland, 22 - 24 July 2008 / [ed] Masoud Motavalli, Dübendorf: EMPA-Akademie , 2008Conference paper (Refereed)
  • 24. Blanksvärd, Thomas
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Shear strengthening of concrete structures with the use of mineral-based composites2009In: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 13, no 1, p. 25-34Article in journal (Refereed)
    Abstract [en]

    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.

  • 25.
    Blanksvärd, Thomas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Mineral based strengthening systems for upgrading RC Structures2012In: Fib symposium Stockholm 2012: concrete structures for sustainble community : proceedings / [ed] Dirch H. Bager; Johan Silfwerbrand, Stockholm: Swedish Conrete Association , 2012, p. 363-366Conference paper (Refereed)
    Abstract [en]

    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.

  • 26.
    Carolin, Anders
    et al.
    Trafikverket, Luleå.
    Anderson, Robert
    Network Rail, London, United Kingdom.
    Heissenberger, Roman
    ÖBB, Wien, Austria.
    Hermosilla Carrasco, Carlos
    Acciona Technology, Madrid, Spain.
    Schewe, Britta
    Deutsche Bahn, Berlin, Germany.
    Nilimaa, jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwircen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Innovative Intelligent Management of Railway Bridges, In2Rail: A European Horizon 2020 Project2016In: IABSE CONGRESS, STOCKHOLM, 2016: Challenges in Design and Construction of an Innovativeand Sustainable Built Environment / [ed] Lennart Elfgren, Johan Jonsson, Mats Karlsson, Lahja Rydberg-Forssbeck and Britt Sigfrid, CH - 8093 Zürich, Switzerland, 2016, p. 2552-2561Conference paper (Refereed)
    Abstract [en]

    Innovative Intelligent Railways, In2Rail, is a European Horizon 2020 Project with the objective to enhance capacity, increase reliability and reduce Life Cycle Costs of European Railways. Bridges and Tunnels is the main focus in Work Package 4. The aim is to study, benchmark and further develop new Inspection Technologies in order to create more proactive maintenance procedures. In this paper some preliminary results are presented.

  • 27.
    Coric, Ibrahim
    et al.
    Trafikverket.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Skanska Sverige.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Norut, Norge.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Railway Bridges on the Iron Ore Line in Northern Sweden– From Axle Loads of 14 to 32,5 ton2018In: IABSE Conference 2018 – Engineering the Past, to Meet the Needs of the FutureJune 25-27 2018, Copenhagen, Denmark: IABSE Reports, Vol 111, 2018, Vol. 111Conference paper (Refereed)
    Abstract [en]

    The Iron Ore Railway Line was built around 1900 and has more than 100 bridges. It has a length of ca 500 km and runs from Kiruna and Malmberget in northern Sweden to the ice-free harbour in Narvik in Norway on the Atlantic and to Luleå in Sweden on the Baltic. The original axle load was 14 ton. The axle load has gradually been increased to 25 ton in 1955, to 30 ton in 1998 and to 32,5 ton in 2017.The increases in axle loads have been preceded by monitoring and assessment studies of the bridges. The capacity and need for strengthening or replacement of the bridges have been evaluated. Many of the bridges could carry a higher load than what it was designed for. Experiences from studies before the axle load was increased in 1998 and 2017 are presented and discussed.

  • 28.
    Duvnjak, Ivan
    et al.
    University of Zagreb, Croatia.
    Bartolak, Marko
    University of Croatia.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Lessons Learnt from Full-Scale Tests of Bridges in Croatia and Sweden2018In: IABSE Symposium, Nantes 2018: Tomorrow's Megastructures, International Association for Bridge and Structural Engineering , 2018, article id S23-127Conference paper (Refereed)
    Abstract [en]

    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 Croatia and Sweden. 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.

  • 29.
    Elfgren, Lennart
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bagge, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Shu, Jiangpeng
    Chalmers University of Technology.
    Plos, Mario
    Chalmers University of Technology, Department of Civil and Environmental Engineering , Chalmers University of Technology.
    Larsson, Oskar
    Faculty of Engineering, LTH, Department of Constructional Sciences, Lund University.
    Sundquist, Håkan
    Kungliga tekniska högskolan, KTH, KTH, Structural Engineering & Bridges.
    Brottbelastning av en 55 år gammal spännbetongbro i Kiruna - Kalibrering av modeller för tillståndsbedömning: Slutrapport till BBT2015Report (Refereed)
    Abstract [sv]

    En 55 år gammal spännbetongbro med fem spann med längden 121,5 m har provats till brott för att studera och kalibrera metoder för tillståndsbedömning av befintliga broar. Projektet harbidragit till att ge svar på flera av de frågor som ställs beträffande hållbart byggande och uppföljning av befintliga konstruktioner inom BBT - Branschprogram för forskning och innovation avseende byggnadsverk inom transportsektorn. Framför allt adresseras följande områden:A.2.1 Säkerhet, robusthet och sårbarhet – En betydande robusthet finns i den studerade typen av broar och säkerheten mot brott är större än den som erhålls med modellerna i de europeiska betongnormerna.A.2.4 Metodik för individuell bärighetsklassning av broar – En kombination av FE-modellering och analytiska studier baserade på verklig geometri och aktuella materialdata har goda förutsättningar att kunna ge betydligt mer kvalificerade bedömningar av kvarvarande bärförmåga än nu tillämpade metoder.A.2.5 Beständighet och livslängd hos nya byggnadsverk – Projektet ger underlag för förbättrade metoder att bestämma beständighet och livslängd hos spännbetongbroar.A.3.1 Mätmetoder – I projektet har en ny metod för fotografisk töjningsmätning provats. Resultaten har ännu inte hunnit helt utvärderas men de ser lovande ut.A.3.2 Bedömning av tillstånd och livslängd – Projektet ger underlag för förbättrade metoder för bedömning av tillstånd och livslängd.Projektet har hittills redovisats i en doktors- och en licentiatavhandling och i tio tidskrifts- och konferensartiklar.

  • 30.
    Elfgren, Lennart
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Project: Mainline-MAINtenance, renewaL and Improvement of rail transport iNfrastructure to reduce Economic and environmental impacts2012Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    - Apply new technologies to extend the life of elderly infrastructure - Improve degradation and structural models to develop more realistic life cycle cost and safety models - Investigate new construction methods for the replacement of obsolete infrastructure- Investigate monitoring techniques to complement or replace existing examination techniques -Develop management tools to assess whole life environmental and economic impact.

  • 31.
    Elfgren, Lennart
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Skanska Sverige AB Technology, Bridge and Civil Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. STO Scandinavia AB.
    Casas, Joan R
    Universitat Politècnica de Catalunya.
    Bell, Brian
    UIC, International Federation of Railways, Paris, Network Rail, London.
    Lundgren, Karin
    Chalmers University of Technology, Department of Civil and Environmental Engineering.
    Guideline for application of new technologies to extend life of elderly rail infrastructure: Deliverable 1.4 in MAINLINE - a project within EC 7tf Framework Programme2015Report (Other (popular science, discussion, etc.))
    Abstract [en]

    There are many traditional technologies available to extend the life of elderly rail infrastructure, some of which are being improved or developed, whilst new technologiescontinue to emerge. In this guideline some of the most promising new or updated technologies are presented forbridges, track and earthwork regarding: - Assessment methods- Repair and Strengthening methodsIn an Appendix strengthening methods are presented in more detail with examples of designcalculations and work carried out.The guideline is based on work presented in earlier reports in MAINLINE: ML-D1.1 (2013):Benchmark of new technologies to extend the life of elderly rail infrastructure, ML-D1.2(2013): Assessment methods for elderly rail infrastructure and ML-D1.3 (2014): Newtechnologies to extend the life of elderly infrastructure; In these reports, backgroundinformation and more references can also be found.

  • 32.
    Elfgren, Lennart
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Load Testing as Part of Bridge Management in Sweden.: Chapter 112019In: Load Testing of Bridges: Proof load Testing and the Future of Load Testing, Volume Editor Eva O. L. Landsoght: Series: Structures and Infrastructures, Vol. 13, Series Editor Dan M. Frangopol, / [ed] Eva O.L. Landsoght (Vol 13), Dan M. Frangopol (Series Editor), London/Leiden: Taylor and Francis Group , 2019, 1, p. 333-346Chapter in book (Refereed)
    Abstract [en]

    Load testing of new and existing bridges was performed regularly in Sweden up to the 1960ies. It was then abandoned due to high costs versus little extra information obtained. Most bridges behaved well in the serviceability limit range and no knowledge of the ultimate limit stage could be obtained without destroying the bridge. At the same time the methods for calculating the capacity developed and new numerical methods were introduced. Detailed rules were given on how these methods should be used. Some decommissioned bridges were tested to their maximum capacity to be able to study their failure mechanisms and to calibrate the numerical methods. In this paper some examples are given on how allowable loads have increased over the years and of tests being performed. Nowadays, load testing may be on its way back, especially to test existing rural prestressed concrete bridges, where no design calculations have been retained

  • 33.
    Elfgren, Lennart
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Bagge, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. WSP, Luleå, Sweden.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Puurula, Arto
    Savonia University of Applied Sciences, Kuopio.
    Häggström, Jens
    Trafikverket, Luleå, Sweden.
    Paulsson, Björn
    Charmec, Chalmers University of Technology.
    Load-testing used for qulity control of bridges2018In: Quality Specifications for Roadway Bridges: Workshop of COST TU 1406 / [ed] José Matos, 2018, p. 1-6Conference paper (Refereed)
    Abstract [en]

    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.

  • 34.
    Huang, Zheng
    et al.
    School of Civil Engineering, Southeast University, Nanjing.
    Lu, Zhitao
    School of Civil Engineering, Southeast University, Nanjing.
    Song, Shoutang
    School of Civil Engineering, Southeast University, Nanjing.
    Tu, Yongming
    School of Civil Engineering, Southeast University, Nanjing.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Infrastructure, Materials and Structures, Norut, Narvik.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Finite element analysis of shear deformation in reinforced concrete shear-critical beams2018In: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 14, no 6, p. 791-806Article in journal (Refereed)
    Abstract [en]

    The objective of this paper was to study the contribution of shear deformation in reinforced concrete (RC) shear-critical beams. A 2D concrete material model based on smeared fixed crack was presented and incorporated into a commercial finite element (FE) software. A method of calculating shear and flexure deformation separately out of total deformation in the shear span was presented and implemented into the FE analysis. Several experiments of RC shear-critical beams were simulated and good agreement between the experimental and numerical results was obtained in terms of total deformation, flexure deformation, shear deformation and crack patterns. The results show that after shear cracking, the contribution of shear deformation to total deformation increases rapidly. The shear span-to-depth ratio, the longitudinal reinforcement, the shear reinforcement and the load level could be the critical factor to influence the contribution of shear deformation. It appears that for RC shear-critical beams without shear reinforcement, the deformational behaviour is governed by flexure deformation. However, for RC beams with shear reinforcement, the contribution of shear deformation is not negligible after shear cracks develop. Moreover, the measuring method could also affect the measured shear deformation. Finally, future work on experimental investigation into this topic is recommended.

  • 35.
    Huang, Zheng
    et al.
    Southeast University, Nanjing, China.
    Tu, Yong-Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Bagge, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Modelling of Damage and its use in Assessment of a PrestressedConcrete Bridge2016In: IABSE CONGRESS, STOCKHOLM, 2016: Challenges in Design and Construction of an Innovativeand Sustainable Built Environment / [ed] Lennart Elfgren, Johan Jonsson, Mats Karlsson, Lahja Rydberg-Forssbeck and Britt Sigfrid, CH - 8093 Zürich, Switzerland, 2016, p. 2093-2108Conference paper (Refereed)
    Abstract [en]

    A five-span prestressed concrete bridge has been subjected to a loading test up to failure in Kiruna, Sweden. The bridge was 55 years old and had a length of 121.5 m. The test has been used to validate and calibrate existing nonlinear finite element programs for predicting the shear behavior of reinforced and prestressed concrete structures. Two 3D finite element (FE) models of the Kiruna Bridge are built in commercial software Abaqus, one using shell-elements and one using a combination of shell and beam elements. Predictions obtained from these two models are well consistent with mode shapes and eigenfrequencies computed from acceleration measurements on the bridge before and after loading it to failure.The shear failure of the bridge is also simulated using the built-in concrete damage plasticity (CDP)model in Abaqus. The predicted load-displacement curve is in good agreement with the measurements. Verification of the CDP model is conducted at element and member level with two different damage parameter evolutions. The verification indicates that the damage parameter will affect the predicted shear behavior. It does not seem to be reliable to adopt the CDP model to simulate the shear behavior in the present research. A long term goal is to use use the measured mode shapes, eigenfrequencies and FE models for evaluating methods for damage identification. Such methods are important for maintenance of different structures, for extending their life span and for better knowledge of their load carrying capacity. The use is described of so-called sparse regularized finite element method updating (FEMU) methods. Some important properties of such methods are demonstrated using simulations on a Kirchhoff plate. For instance, the simulations suggest that both eigenfrequencies and mode shapes should be used for precise localization of the damage.

  • 36.
    Huang, Zheng
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, Nanjing, China.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, Nanjing, China.
    Meng, Shaoping
    School of Civil Engineering, Southeast University, Nanjing, China.
    Bagge, Niklas
    Department of Bridge & Hydraulic Design, WSP Sverige AB, Gothenburg, Sweden.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Validation of a numerical method for predicting shear deformation of reinforced concrete beams2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 197, article id 109367Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to validate a 2D nonlinear finite element (FE) model for estimating the post-cracking shear deformation of reinforced concrete (RC) beams. The proposed FE model treated the cracked concrete as an orthotropic material in the framework of the fixed-crack approach. The experimental data for both the overall response (including the total and shear-induced deflection) and the detailed response (including the mean shear strain, mean vertical strain and principal compressive strain angle) of five I-section RC beams, monitored by the main authors of this paper with the Digital Image Correlation technique, were used to verify the proposed model. In addition, 27 further test beams evaluated in independent research programs were collected to assemble a database. The proposed FE model was further verified against the database. Two additional FE models (the rotating-crack model developed in this work and Response-2000 developed by Bentz (2000)) were also evaluated by simulating the detailed responses of the beams in the database. The results obtained validate the proposed FE model for predicting the post-cracking shear deformation of RC beams and indicate that the proposed FE model is more suitable for simulating the shear behaviour of RC beams than the rotating-crack model or Response-2000.

  • 37.
    Häggström, Jens
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Bagge, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Puurula, Arto
    Savonia University of applied Sciences, Kuopia, Finland.
    Rydberg-Forssbeck, Lahja
    Trafikverket, Stockholm.
    Carolin, Anders
    Trafikverket, Luleå.
    Testing Bridges to Failure: Experiences2017In: IABSE Symposium, Vancouver, 2017: Engineering the Future, Zürich, Switzerland: IABSE - International Association for Bridges and Structural Engineering , 2017, p. 2832-2839Conference paper (Refereed)
    Abstract [en]

    Four bridges of different types have been tested to failure and the results have been compared to the load-carrying capacity calculated using standard code models and advanced numerical methods. The results may help to make accurate assessments of similar existing bridges. Here it is necessary to know the real behaviour, weak points, and to be able to model the load-carrying capacity in a correct way.

    The four bridges were: (1) a one span steel truss railway bridge; (2) a two span strengthened concrete trough railway bridge; (3) a one span concrete trough bridge tested in fatigue; and (4) a five span prestressed concrete road bridge.

    The unique 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.

  • 38.
    Häggström, Jens
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Assessment and full scale failure test of a steel truss bridge2015In: IABSE Workshop Helsinki 2015: Safety, Robustness and Condition Assessments of Structures, Zürich: International Association for Bridge and Structural Engineering, 2015, p. 288-295Conference paper (Refereed)
    Abstract [en]

    Large amount of resources has been invested in maintaining existing infrastructure. Several of thesestructures are now becoming old and do not meet the requirements of today or are reaching the endof their lifecycle. It is not possible to replace all of these structures that are deemed or are about tobe deemed obsolete, due to high cost and environmental impacts.One way to keep these structures in use for a longer time is innovative and intelligent assessment ofthe actual state of stress and behaviour. In such cases, using structural health monitoring to assessthe structure might be an efficient way to extend the life of the structure.This paper will describe a unique monitoring program over two similar 33 m long steel trussbridges situated in Sweden. One of these bridges, Aby River, had a regulated axle load of 25 tonsand was tested to failure in 2013. The other bridge, Rautasjokk, has a regulated axle load of 30 tonswhich will be upgraded to 32.5 tons and will be in use for the coming years.The monitoring program was performed as; monitoring of the bridge over Aby river when it wasstill in service. After replacement the old bridge was moved and tested under static loads to assessboundary conditions and state of stress. Parts of this bridge were then disassembled to be tested formaterial properties and fatigue capacity. A theoretical assessment of the Rautasjokk bridge was thenperformed based on the conclusions from the measurements on the Aby bridge. Finally the plan isto verify findings by performing measurements on live loading for the Rautasjokk bridge in servicelimit state.The aim for this project is to verify the continuous safety for the Rautasjokk bridge by using inputfrom tests performed at both bridges.

  • 39.
    Häggström, Jens
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Collin, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Fatigue assessment of stringer beams using structural healthmonitoring2016In: 19th IABSE Congress Strockholm 21-23 September 2016: Challenges in Design and Construction of an Innovative ans Sustainable Built Environment / [ed] ennart Elfgren, Johan Jonsson, Mats Karlsson, Lahja Rydberg-Forssbeck and Britt Sigfrid, CH - 8093 Zürich, Switzerland, 2016, p. 1455-1462Conference paper (Refereed)
    Abstract [en]

    Fatigue assessment of existing bridges is often carried out through simple calculations where the nominalstress range is compared with the fatigue strength based on a number of detail categories specified incodes. Presented in this paper, is the stepwise fatigue assessment through measurements of the 60 yearold bridge over Rautasjokk located in northern Sweden. According to the code‐based assessment of thestringers, it has already exceeded its lifetime about four times; however no cracks have been identified. Bymeasuring strains the real state of stress was identified, where both nominal stresses and local approacheshave been evaluated and compared. Even though the local approach should provide a better accuracy incomparison with the nominal stresses, this approach was only favorable for one out of the three studiedlocations.

  • 40.
    Häggström, Jens
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Collin, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Southeast University, School of Civil Engineering, Nanjing.
    Full-scale testing to failure of a steel truss railway bridge2017In: Proceedings of the Institution of Civil Engineers: Engineering Sustainability, ISSN 1478-4637, E-ISSN 1751-7664, Vol. 170, no 2, p. 93-101Article in journal (Refereed)
    Abstract [en]

    Significant resources have been invested in maintaining existing infrastructure. Many structures are becoming old, do not meet current requirements, or are reaching the end of their life cycle. It is not feasible or sustainable to replace all of those that may be deemed obsolete; however, often their specified capacities are very conservative. So there is an urgent need to obtain more robust knowledge of their true status. This paper describes a unique project, in which a 33 m long steel truss railway bridge (over the Åby River) was tested to failure. The findings can be used to identify optimal solutions for other bridges of the same design that are still in use, notably the bridge over Rautasjokk (a river in Sweden). These two bridges were tested in three stages. This paper focuses on the second stage, wherein Åby Bridge was subjected to static full-scale testing to failure, by pulling it downwards. The global failure mode consisted of buckling of the top chord with yielding of the steel starting at a total load of 8 MN and the peak load being reached at around 11 MN, corresponding to a load approximately four to five times higher than the characteristic design load.

  • 41.
    Häggström, Jens
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Skanska Teknik, Göteborg.
    Collin, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Ramböll Sverige AB, Luleå.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Assessment and full scale failure test of a steel truss bridge2015In: IABSE symposium Madrid 2014: Engineering for progress, nature and people, Zürich: International Association for Bridge and Structural Engineering, 2015, p. 2757-2764Conference paper (Refereed)
    Abstract [en]

    Large amount of resources has been invested in maintaining existing infrastructure. Several of these structures are now becoming old and do not meet the requirements of today or are reaching the end of their lifecycle. It is not possible to replace all of these structures that are deemed or are about to be deemed obsolete, due to high cost and environmental impacts.One way to keep these structures in use for a longer time is innovative and intelligent assessment of the actual state of stress and behaviour. In such cases, using structural health monitoring to assess the structure might be an efficient way to extend the life of the structure.This paper will describe a unique monitoring program over two similar 33 m long steel truss bridges situated in Sweden. One of these bridges, Aby River, has a regulated axle load of 25 tons and is deemed to have reached is end of life due to fatigue. The other bridge, Rautasjokk, has a regulated axle load of 30 tons but will be in use for the coming years.The monitoring program has the following outline; monitoring of the bridge over Aby river when it is in service, after replacement this bridge will be moved and tested under static loads to assess boundary conditions and state of stress, then parts of this bridge will be disassembled and these parts will be tested in laboratory environment for fatigue life assessment, all of these results will then be controlled by monitoring of the bridge over Rautasjokk in service limit state.The outline of this project will give input for the fatigue life models that are used today and probably upgrade the fatigue life of the bridge over Rautasjokk.

  • 42.
    Häggström, Jens
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Bridge over Åby River: Evaluation of full scale testing2017Report (Other academic)
  • 43.
    Johnsson, Helena
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Carolin, Anders
    Glulam members strengthened by carbon fibre reinforcement2007In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 40, no 1, p. 47-56Article in journal (Refereed)
    Abstract [en]

    Glulam members often become large in cross section where heavy loads should be carried. In some applications this may cause problems if limitations on height are posed. A possible solution is to reinforce the member by e.g. bonding fibre reinforced polymer (FRP) on the beams or between the glulam lamellas. The aim of this paper is to investigate the possibility of strengthening glulam beams by the use of pultruded rectangular carbon fibre rods and to establish the anchoring length for this system. Tests were performed in three different series completed by a reference series, 10 specimens altogether. All tests were performed as short-term experiments in four-point bending. The experimental results were compared to analytical models in several aspects. The overall capacity of the beam was established using an analogy with concrete beams. Special attention was made to establishing the anchoring length of the reinforcement bar, since this is governing to avoid premature failures. The anchorage length was tested and an analytical model established. The agreement between the analytical critical anchoring length and the test result was satisfactory. The proposed reinforcement method increased the short-term flexural load-carrying capacity by 49-63% on average.

  • 44.
    Mahal, Mohammed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    A two-scale damage model for high-cycle fatigue at the fiber-reinforced polymer-concrete interface2016In: Computers and Concrete, ISSN 1598-8198, Vol. 116, p. 12-20Article in journal (Refereed)
    Abstract [en]

    This paper presents a new two-scale damage model of the fiber-reinforced polymer (FRP)-concrete bond under high-cycle fatigue. The material behavior is modeled as elastic-plastic coupled with damage for the microscale analysis and as elastic for the mesoscale analysis. A new damage law for the interface joint is described. The two-scale damage model has been implemented as a material model for a three dimensional an eight-node interface element of zero thickness and used to simulate a double shear joint specimen under high cycle fatigue. The numerical calculations were performed with a full incremental cycle solution and a new cycle jump approach. Comparing the results from the finite element method (FEM) model with experimental data shows that the model is capable of accurately predicting the cyclic fatigue loading slip response of the joint interface.

  • 45.
    Mahal, Mohammed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Examination at a material and structural level of the fatigue life of beams strengthened with mineral or epoxy bonded FRPs: the state of the art2013In: Advances in Structural Engineering, ISSN 1369-4332, E-ISSN 2048-4011, Vol. 16, no 7, p. 1329-1345Article in journal (Refereed)
    Abstract [en]

    This paper presents a state of the art review of different material combinations and applications of mineral-based and epoxy-based bonded Fiber Reinforced Polymers (FRP), used for the strengthening of concrete structures subjected to fatigue loading. In this review, models of the fatigue life at the material and structural level are presented. This study examines the mechanical behavior of the FRP-material, surface bonding behavior and concrete beams strengthened under fatigue loading with different types of FRP-systems. The parameters that are investigated are applied load value, time dependent effects, type of strengthened structures (shear, flexural or combined) and the configuration of sheets or plates. The building codes and researchers' recommendations are also discussed. As a result of this review, the reader will obtains an overview of suitable materials and methods for strengthening structures subjected to fatigue loading by referring to the estimated fatigue life of material and strengthening structures at various applied stress levels.

  • 46.
    Mahal, Mohammed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    FE modeling of FRP-concrete interface for very high cycle fatigue behavior2014In: Advances in fracture and damage mechanics XII: selected, peer reviewed papers from the 12th International Conference on Fracture and Damage Mechanics (FDM 2013), September 17 - 19, 2013, Sardinia, Italy / [ed] A. Milazzo; M.H. Aliabadi, Durnten-Zurich: Trans Tech Publications Inc., 2014, p. 165-168Conference paper (Refereed)
    Abstract [en]

    The fatigue damage of FRP-concrete interface is a major problem in strengthened structures subjected to fatigue loading. The available FRP-concrete interface models published in the literature usually deal with fracture mechanism approach, which is unsuitable for high cycle fatigue damage. In this study, a constitutive micro model is developed for FRP-concrete interface for high cycle fatigue and incorporated into a three dimensional finite-element program. Numerical analysis of a double lap joint is carried out, and the results show that the proposed model is reasonably accurate

  • 47.
    Mahal, Mohammed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sas, Gabriel
    Northern Research Institute.
    Using digital image correlation to evaluate fatigue behavior of strengthened reinforced concrete beams2015In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 105, p. 277-288Article in journal (Refereed)
    Abstract [en]

    The fatigue behavior of reinforced concrete beams externally strengthened with carbon fiber reinforced polymer plates and near-surface mounted bars has been investigated using a digital image correlation (DIC) technique. Displacement fields obtained from digital images recorded during specific load cycles in fatigue tests are analyzed to provide information on crack width, beam deflection and curvature, and major principal strains to enable crack detection. The results obtained in this way were compared to data gathered using conventional sensors, revealing that the DIC technique provided very accurate and detailed information. The experimental results for plate-strengthened, bar-strengthened, and unstrengthened beams are discussed.

  • 48.
    Mahal, Mohammed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Experimental performance of RC beams strengthened with FRP materials under monotonic and fatigue loads2016In: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 122, p. 126-139Article in journal (Refereed)
    Abstract [en]

    Carbon fiber-reinforced polymers (CFRPs) are increasingly being used to repair and strengthen reinforced concrete (RC) bridge members. CFRP strengthening may be applied by bonding polymeric plates to the exterior of the member’s tension surface or by placing CFRP bars inside the concrete member cover to provide near-surface mounted reinforcement. It is not clear which of these approaches is most effective at resisting fatigue loads. To compare their efficacy, four-point bending tests with reinforced concrete beams were conducted under monotonic and fatigue loading using both strengthened and unstrengthened RC beams having steel reinforcements with identical stress levels. The influence of the strengthening material’s properties and prior cracking of the member are investigated and discussed by analyzing failure mechanisms, load-deflection curves, and strain measurements for steel bars and CFRP materials observed during loading experiments. The results obtained indicate that the efficiency of strengthening is primarily determined by the relief of local stress in the member’s reinforcing steel bars before they rupture, and the fatigue life of the reinforcing steel after its initial fracturing. The latter of these quantities is related to the strengthened member’s ability to absorb the energy released at the moment the reinforcing bar fractures.

  • 49.
    Mahal, Mohammed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Fatigue analysis of RC beams strengthened in flexure using CFRP2016In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085Article in journal (Refereed)
    Abstract [en]

    The increasing use of Fiber Reinforced Polymers (FRP) to repair, strengthen or upgrade reinforced concrete (RC) structural elements means that there is a need to develop analytical methods for analyzing the behavior of strengthened members under fatigue loading. This paper describes an analytical model for simulating the fatigue behavior of RC beams strengthened with Carbon Fiber Reinforced Polymer (CFRP). Fatigue calculations are performed using a lamellar model that considers the fatigue behavior of the RC and CFRP strengthening materials during loading. The model’s output is compared to experimental data for four CFRP-strengthened beams, showing that the new model accurately predicted the deflection and strain of each one. In addition, various models for predicting the fatigue life of CFRP-strengthened RC beams were tested and a model capable of providing conservative fatigue life estimates was identified.

  • 50.
    Malaga, Katarina
    et al.
    CBI Betonginstitutet.
    Tammo, Kristian
    CBI Betonginstitutet.
    Flansbjer, Mathias
    SP Technical Research Institute of Sweden.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Peterson, Örjan
    Strängbetong.
    Textile reinforced concrete sandwich panels2012In: Fib symposium Stockholm 2012: concrete structures for sustainble community : proceedings / [ed] Dirch H. Bager; Johan Silfwerbrand, Stockholm: Swedish Conrete Association , 2012, p. 169-172Conference paper (Refereed)
    Abstract [en]

    The main reason for the thickness of a concrete sandwich element is the requirement for the protective concrete cover for the steel reinforcement. By changing the steel reinforcement to non-corrosive textile fibre net this requirement could be strongly reduced. Use of textile reinforced concrete (TRC) makes it possible to produce much thinner and slimmer concrete facades in the future without changing their mechanical properties. This article presents selected results from Tekocrete project (Formas-BIC) concerning pilot production, modelling and full-scale testing of new light weight sandwich elements reinforced with AR glass and carbon fibre nets.

123 1 - 50 of 103
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