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  • 1.
    Bergström, Markus
    et al.
    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.
    Carolin, Anders
    Failure load test of a CFRP strengthened railway bridge in Örnsköldsvik, Sweden2009In: Journal of Bridge Engineering, ISSN 1084-0702, E-ISSN 1943-5592, Vol. 14, no 5, p. 300-308Article in journal (Refereed)
    Abstract [en]

    The results obtained when performing a load test to failure of an existing structure are valuable when assessing calculation models, updating finite element models, and investigating the true structural behavior. In this paper a destructive testing and monitoring of a railway bridge in Örnsköldsvik, Sweden is presented. In this particular test the shear capacity of the concrete girders was of primary interest. However, for any reasonable placement of the load (a line load placed transverse to the track direction) a bending failure would occur. This problem was solved by strengthening for flexure using carbon fiber reinforced polymer (CFRP) rectangular rods epoxy bonded in sawed up slots, e.g., near surface mounted reinforcement. The strengthening was very successful and resulted in a desired shear failure when the bridge was loaded to failure. The load-carrying capacity in bending for the unstrengthened and strengthened bridge as well as the shear capacity was predicted with Monte Carlo simulations. The particular calculation presented showed that there was a 25% probability of a bending failure instead of a shear failure. Monitoring showed that the strengthening reduced the strain in the tensile steel reinforcement by approximately 10%, and increased the height of the compressed zone by 100 mm. When the shear failure occurred, the utilization of the compression concrete and CFRP rods were 100 and 87.5%, respectively. This indicates that a bending failure indeed was about to occur, even though the final failure was in shear.

  • 2. 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

  • 3. 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)
  • 4.
    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.

  • 5. 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)
  • 6. 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.

  • 7.
    Carolin, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Carbon fibre reinforced polymers for strengthening of structural elements2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is a large need for strengthening of concrete structures all around the world. There can be many reasons for strengthening, increased loads, design and construction faults, change of structural system, and so on. The need exists for both strengthening in flexure as well as in shear. Plate bonding with Carbon Fibre Reinforced Polymers, CFRPs has shown to be a competitive method for upgrading existing structures load bearing capacity. When applying composites for increased shear capacity, special concerns need to be taken for design with truss model. A limitation factor of approximately 0.6 must be used due to linear elastic behaviour. When limitation on maximum strain in concrete is applies, the allowable strain in the composite will be even lower due to anisotropy and divergence in fibre and principal strain direction. By bonding CFRP to a structure in sawn grooves some advantages compared to traditional plate bonding may be achieved. It is also found that a structure may be strengthened with live loads during strengthening process. CFRP plate bonding may further be used for strengthening for increased buckling load bearing capacity for steel members subjected to compression and a design proposal is presented. Suggestions for further research are identified and presented.

  • 8. Carolin, Anders
    Improvement of the load-bearing capacity of existing bridges: a review of literature1999Report (Other academic)
    Abstract [en]

    Improvement of load-bearing capacity of bridges is a large subject. Many methods have been developed for strengthening and for increasing the bearing capacity. Two examples are the use of post-tensioning reinforcement and externally bonded carbon fibre products. There is an accelerated increase in the number of objects being strengthened. Especially the method by bonding of carbon fibre is a fast growing technique.

  • 9. Carolin, Anders
    Monitoring of a rail road bridge strengthened with CFRP1999In: Proceedings: nordic concrete research meeting : Reykjavik, Iceland 1999, Oslo: Norsk Betongforening , 1999Conference paper (Refereed)
  • 10.
    Carolin, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Strengthening of concrete structures with CFRP: shear strengthening and full scale applications2001Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Structures can be in need of strengtheing due to many reasons, which are presented in this thesis. A literature review gives the existing methods for enhancing a structures load bearing capacity. In this thesis focus will be set at external bonding with carbon fibre reinforced polymers. A theory for shear strengthing is presented and compared to laboratory test. Full-scale applications with measurements are evaluated and presented. Finally, some topics for further research are given.

  • 11.
    Carolin, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Load-carrying capacity of concrete structures loaded in shear and torsion2002Report (Other academic)
    Abstract [en]

    The report is a state-of-the-art-report about load-carrying capacity in shear and torsion for concrete members.

  • 12. Carolin, Anders
    et al.
    Nordin, Håkan
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Concrete beams strengthened with near surface mounted reinforcement of CFRP2001In: FRP Composites in Civil Engineering: Proceedings of the International Conference on FRP Composites in Civil Engineering, Amsterdam: Elsevier, 2001, Vol. 2, p. 1059-1066Conference paper (Refereed)
    Abstract [en]

    The size of loads wearing on the railroad and highway systems have increased in recent years. For concrete structures with a very long life and also under difficult conditions, it is not uncommon that measures must be taken to improve the structure's durability or its load bearing capacity. Recently, the use of advanced composites in external bonding of extra reinforcement has become an accepted method. However, there are some drawbacks to this method, including that the pretreatment of the concrete surface is highly work intensive and time consuming, as well as quality concerns. With the improved plate bonding presented in this paper, the aforementioned problems are less troublesome. The technique has also been tested with a cementitious bonding agent.

  • 13. Carolin, Anders
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Experimental study of strengthening for increased shear bearing capacity2005In: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 9, no 6, p. 488-496Article in journal (Refereed)
    Abstract [en]

    The need for structural rehabilitation of concrete structures all over the world is well known, and a great amount of research is going on in this field. The use of carbon fiber-reinforced polymer (CFRP) plate bonding has been shown to be a competitive method with regard to both structural performance and economic factors. This method consists of bonding a thin carbon-fiber laminate or sheet to the surface of the structure to act as an outer reinforcement layer. However, most research in this area has been undertaken to study flexural behavior. This paper deals with shear strengthening of reinforced concrete members by use of CFRP. Tests on rectangular beams 3.5 to 4.5 m long have been undertaken to study different parameters, such as fatigue, anchorage, and others. The strain field in shear spans of beams simultaneously subjected to shear and bending is also studied. The tests presented also contribute to the existing literature on tests of concrete members strengthened for increased shear capacity.

  • 14. Carolin, Anders
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Probabilistic design of FRP strengthening of concrete structures2008In: High Performance Structures and Materials IV: [proceedings of the Fourth International Conference on High Performance Structures and Materials (HPSM), which was held in the Algarve, Portugal, in May 2008] / [ed] W.P. De Wilde; C.A. Brebbia, Southampton: WIT Press, 2008, p. 481-489Conference paper (Refereed)
    Abstract [en]

    For a long period of time CFRP plate bonding has been shown to be a competitive method for shear strengthening, both in regards to structural performance and economical aspects. A handful of models for design that include different strengthening aspects exist. Most proposals are derived from assumptions made for the design of new structures and are also based on a deterministic approach where in the best cases a safety factor is added. The use of probabilistic methods is extending and reliability of a designed structure is sometimes calculated. This paper presents how the reliability should be used in the design for strengthening an existing structure, which issues should be considered and also what safety one can expect from a structure strengthened in shear. Partial coefficients on material properties and loads are used to give a uniform treatment of the risk of failure. When partial coefficients are chosen, the reason for strengthening and the strengthening method may be considered to achieve an optimal strengthening with respect to structural safety and economy. The results from the analysis indicate design models for shear strengthening should be analytically determined with a transparent strategy for the uniform treatment of reliability aspects.

  • 15. Carolin, Anders
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Strengthening of a concrete railroad bridge with carbon fibre sheets1999In: Structural faults + repair-99: 8th international conference, London, UK, 13 - 15 July 1999 / [ed] M. C. Forde, Edinburgh: Engineering Technics Press , 1999Conference paper (Refereed)
  • 16. Carolin, Anders
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Theoretical study of strengthening for increased shear bearing capacity2005In: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 9, no 6, p. 497-506Article in journal (Refereed)
    Abstract [en]

    In recent years, the use of carbon fiber reinforced polymer (CFRP) has been shown to be a competitive method for strengthening both the structural and economic performance of concrete. The method has been used for almost a decade, yet – most research undertaken has studied the flexural behavior of strengthened structures, while research on shear strengthening has been limited. The work presented in this paper focuses on CFRP shear strengthening of concrete beams. The theory presented addresses the limitations of the widely used truss model, and a refinement is suggested. A reduction factor to consider the nonuniform strain distribution over the cross section is proposed and strain limitations are prescribed for the principal strain in the concrete instead of the fiber strain, as in previous studies. The derived analytical model is compared to experimental data from tests. Fairly good agreement is found between results from tests and calculated values from theory with regard to both shear-bearing capacity and average fiber utilization.

  • 17. Carolin, Anders
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Undersökning av friktionsförband i trä genom förspända kolfiberbultar2006Report (Other academic)
    Abstract [sv]

    Vasaskeppet bärgades 1961 och är unik i storlek och skick. Av flera anledningar önskas befintliga stålbultar, vilka utgör en del av befintligt förband i skeppet, ersättas. En möjlighet är att ersätta befintliga bultar med bultar av kolfiberkomposit. I denna rapport redovisas resultat från försök där möjligheten till att använda kolfiberbultar för Vasas sammanfogning studerats. Två olika bultsystem har undersökts utifrån lämplighet med avseende på bärförmåga, handhavande samt flexibilitet. Försöksuppställning har utformats utifrån tänkt verkningssätt i skeppet. Ett av bultsystemet har bedömts lämpligare varför utökad provning genomförts på detta system. Laboratorieförsöken visar på att det är fullt möjligt att ersätta stålbultarna i Vasaskeppet med bultar av kolfiberkomposit.

  • 18. Carolin, Anders
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hejll, Arvid
    Concrete beams exposed to live loading during carbon fiber reinforced polymer strengthening2005In: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 9, no 2, p. 178-186Article in journal (Refereed)
    Abstract [en]

    The need for structural rehabilitation of concrete structures all over the world is well known. Extensive amounts of research have been carried out and are ongoing in this field. Most of the laboratory research has been undertaken on structural elements without live load during the strengthening process. Normally owners of structures want to continue their activity or service during strengthening. Full-scale applications have shown that this is possible, but there is a lack of understanding as to how cyclic loads are distributed during strengthening; for example, traffic loads affect the final strengthening result. This paper presents laboratory tests on concrete beams strengthened with carbon fiber-reinforced polymer laminates and near-surface mounted reinforcement. The beams were subjected to a cyclic load during setting of the adhesive, and after additional hardening were then loaded by deformation control up to failure.

  • 19.
    Carolin, Anders
    et al.
    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.
    Nilsson, Martin
    Enochsson, Ola
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Fahleson, Claes
    Tillförlitlighetsanalys för reparerade eller förstärkta byggnadskonstruktioner2004Report (Other academic)
    Abstract [sv]

    I rapporten visas på möjligheterna med att använda tillförlitlighetsanalys på byggnadskonstruktioner som förstärks. I det stora fokuseras på betongkonstruktioner och särskilt diskuteras förstärkning av betongkonstruktioner med hjälp av utanpåliggande kolfiberkompositmaterial. Förstudien visar att tillförlitlighetsanalys i generella termer kan vara mycket användbart när det gäller att studera bärförmågan samt vilken konsekvens detta har för den befintliga konstruktionen, speciellt tydligt blir detta när det kopplas till verkliga objekt. Utöver detta visar studien på möjligheter att på ett mer nyanserat sätt förstärka konstruktioner där tillförlitlighetsanalys är ett viktigt verktyg. Studien visar också på behov av fortsatt forskning, speciellt tydligt är detta när det gäller vilka värden samt vilka partialkoefficienter man ska välja för de nya materialen som börjar användas, dvs. för kompositmaterial. I tillägg till detta behöver en nyanserad studie göras gällande de beräkningsmodeller som används i samband med förstärkning och även avseende på de brottmoder som kan uppstå.

  • 20. Carolin, Anders
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Åström, Lars
    Konstruktionsprovning av stålrör2003Report (Other academic)
    Abstract [sv]

    Under 2002 och 2003 genomfördes vid Luleå tekniska universitet, Avdelningen för Konstruktionsteknik en studie av stålrör uppstyvade med kol-, aramid- respektive glasfiberkomposit för att på så sätt öka knäcklasten. De metoder som användes var handuppläggning samt montage av förtillverkade skal tillverkade genom vakuuminjicering. Totalt provades nio stålrör vardera med längden 3.800 mm och diameter 88,9 mm. Ett rör lämnades oförstärkt och användes som referens. Resultatet från provningen visade att det var möjligt att öka knäcklasten genom att använda metoden med utanpåliggande fiberkomposit. I samband med undersökningen har även en analytisk och numerisk modellering av försöken gjorts. Denna stämmer bra överens med försöken. Förutom försök i laboratorium och teoretiska analyser utfördes en praktisk studie om gällande möjligheten att förstärka stålrör i fält. Denna undersökning gjordes hos Spännarmering AB i Upplands Väsby. Det visade sig att metoden med förtillverkade rör var att föredra framför handuppläggning. Dock bör speciella verktyg tas fram för att applicera lim på en mast i fält.

  • 21. Carolin, Anders
    et al.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Vill vi betala mer för ökad dammsäkerhet?2007In: Norrbottens-Kuriren, p. 3-Article in journal (Other (popular science, discussion, etc.))
  • 22.
    Demeter, Istvan
    et al.
    Politechnica University of Timisoara.
    Nagy-György, Tamas
    Politechnica University of Timisoara.
    Stoian, Valeriu
    Politechnica University of Timisoara.
    Daescu, Cosmin
    Politechnica University of Timisoara.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Seismic retrofit of precast RC wall panels with cut-out openings using FRP composites2009In: The 9th International Symposium on Fiber-Reinforced Polymer Reinforcement for Concrete Structures (FRPRCS-9) / [ed] D. J. Oehlers; M.C. Griffith; R. Seracino, Adeleide: University of Adelaide , 2009Conference paper (Refereed)
    Abstract [en]

    The present study was conceived in order to investigate the shear behaviour of the Precast Reinforced Concrete Wall Panels (PRCWP) with cut-out openings subjected to in-plane seismic loading conditions and to assess the shear capacity gain obtained using Fiber Reinforced Polymer (FRP) composites as retrofit solution. The structural system of Precast Reinforced Concrete Large Panels (PRCLP) was extensively used in Romania, from 1950 to 1990, for housing buildings with 5 and 9 stories. Cut-out openings are often required to facilitate direct access from outside or between adjacent apartments, predominantly at the ground floor, where both gravity and seismic capacity demand is maximum. However, cut-out openings performed in structural walls results in the modification of the internal force flow paths, loss of load bearing capacity and reduced structural safety. Similar experimental researches are scarce in the literature. The earthquake resisting behaviour of Reinforced Concrete (RC) structural walls with openings, strengthened by Carbon FRP (CFRP) sheets and grids, was investigated in the post-damage repair and strengthening case. The shear and flexural strengthening effect of differently oriented CFRP sheets was examined on cantilever type RC shear walls in both prior-to-damage and post-damage situations. Experimental research was performed on high slenderness RC walls with door openings distributed on four height levels, strengthened with CFRP sheets.

  • 23. Elfgren, Lennart
    et al.
    Täljsten, Björn
    Carolin, Anders
    Eriksen, Jörgen
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Guidelines for strengthening of railway bridges2009In: Proceedings of Workshop: COST Action C25 : Sustainability of Constructions - Integrated Approach to Life-time Structural Engineering / [ed] Luís Bragança, 2009, p. 141-145Conference paper (Refereed)
    Abstract [en]

    In the international project "Sustainable Bridges", one of the deliverables is a design guide for strengthening of bridges. This paper gives the reader a first look into this guidelinewhich can be found at the projects website: www.sustainablebridges.net

  • 24. Hejll, Arvid
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Structural health monitoring of the Gröndals bridge in Sweden: the behaviour of CFRP strengthening in cold temperature2006In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 6176, no 17Article in journal (Refereed)
    Abstract [en]

    To obtain a better knowledge of existing structures behaviour monitoring can be used. The use of monitoring in bridge structures by the use of instruments to assess the integrity of structures is not new and there are reports from structures tested as early as in the 19th century according to ISIS Canada1 However, the term SHM (Structural Health Monitoring) is relatively new to civil engineering and the driving force to implement SHM comes from recognising the limitations of conventional visual inspections and evaluations using conservative codes of practice. The possibilities to monitor existing structures with help of the rapidly evolving Information Technology are to day carried out. The objective of SHM is to monitor the in-situ behaviour of a structure accurately and efficiently, to assess its performance under various service conditions, to detect damage or deterioration, and to determine the health or condition of the structure1. In Sweden strengthening and periodic monitoring of a large freivorbau bridge (pre-stresed concrete box girder bridge) has been carried out, the Gröndals Bridge. The bridge is located in Stockholm and is approximately 400 m in length with a free span of 120 m. It was opened to tram traffic in year 2000. Just after opening cracks were noticed in the webs, these cracks have then increased, the size of the largest cracks exceeded 0.5 mm, and at the end of year 2001 the bridge was temporarily strengthened. This was carried out with externally placed prestressed steel stays. The reason for cracking is quite clear but the responsibility is still debated. Nevertheless, it was evidently that the bridge needed to be strengthened. The strengthening methods used were CFRP plates in the Service Limit State (SLS) and prestressed dywidag stays in the Ultimate Limit State (ULS). The strengthening was carried out during year 2002. At the same time monitoring of the bridge commenced, using LVDT crack gauges as well as optical fibre sensors. This monitoring was carried out during the summer period. In addition to this a winter monitoring was carried out in the beginning of 2005. This paper presents the background to strengthening and a comparison between summer and winter monitoring where the strengthening behaviour between the two seasons is enlightened. The result from the monitoring is very interesting; it would have been preferable to strengthen the bridge during the winter.

  • 25.
    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.

  • 26.
    Nilimaa, Jonny
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Paulsson, Björn
    Trafikverket.
    Extended Life of Railway Bridges. Results from EC-FP7-project MAINLINE2013In: Assessment, Upgrading and Refurbishment of Infrastructures: IABSE Conference Rotterdan 2013 / [ed] Philippe Van Bogaert, Zürich: International Association for Bridge and Structural Engineering, 2013, p. 314-315Conference paper (Refereed)
    Abstract [en]

    There is a need to extend the life of many existing railway bridges. To facilitate this is one of the objects of the EC-FP7-Project MAINLINE, covering a period from 2011 to 2014. Three case studies are presented in which existing bridges are being studied in order to extend their life length: First a concrete trough bridge strengthened with post stressed bars in drilled holes through the slab is considered; followed by another concrete trough bridge strengthened with sawn in Near Surface Mounted Reinforcement (NSMR) of Carbon Fibre Reinforce Polymers (CFRP); and finally a steel truss bridge which will be loaded to failure to calibrate the assessment methods.

  • 27.
    Nilimaa, Jonny
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Paulsson, Björn
    UIC, Trafikverket.
    Extending the life of elderly rail bridges by strengthening2014In: 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. 1082-1088Conference paper (Refereed)
    Abstract [en]

    There is a need to extend the life of many existing railway bridges. To facilitate this is one of the objects of the EC-FP7-Project MAINLINE, covering a period from 2011 to 2014. New or improved technologies are investigated to help with this. For bridges, the most promising techniques are enhanced inspection, assessment and strengthening methods. Case studies are presented where three different strengthening techniques have been applied to existing concrete trough bridges. First, sawn in Near Surface Mounted Reinforcement (NSMR) of Carbon Fibre Reinforce Polymers (CFRP) are used; followed by a bridge where carbon fibre cables were drilled through the bridge and finally a bridge was strengthened with post tensioned bars in drilled holes through the slab in the transverse direction. All three methods proved to be very successful.

  • 28.
    Nilimaa, Jonny
    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.
    Bagge, Niklas
    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.
    Ohlsson, Ulf
    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.
    Carolin, Anders
    Paulsson, Björn
    UIC, Trafikverket.
    Maintenance and Renewal of Concrete Rail Bridges: Results from EC project MAINLINE2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 25-28Article in journal (Refereed)
    Abstract [en]

    There is a need to extend the life and capacity of many existing railway bridges. One of the objects of the EC-FP7-Project MAINLINE, 2011-2014, is to facilitate this. Guidelines for assessment and strengthening methods are presented as well as case studies in which existing bridges are being studied in order to extend their life length. Case studies on bridges tested to failure in order to calibrate assessment methods are also presented. Fatigue is often a vital question. A Life Cycle Assessment Tool (LCAT) is being prepared to enable Infrastructure Managers to choose optimal maintenance strategies.

  • 29.
    Nilimaa, Jonny
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sabau, Cristian
    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.
    Puurula, Arto
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Savonia University.
    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. Skanska.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Carolin, Anders
    Trafikverket.
    Paulsson, Björn
    Charmec Railway Center.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Assessment and Loading to Failure of Three Swedish RC Bridges2018In: Evaluation of Concrete Bridge Behavior through Load Testing: International Perspectives / [ed] Eva Lantsoght and Pinar Okumus, Faarmington Hills, MI: American Concrete Institute, 2018, Vol. 323, p. 8.1-8.18, article id SP-323-8Chapter in book (Refereed)
    Abstract [en]

    Current codes often underestimate the capacity of existing bridges. The purpose of the tests presented here has been to assess the real behaviour and capacity of three types of bridges in order to be able to utilize them in a more efficient way.

    The three studied bridges are: (1) Lautajokk – A one-span trough bridge tested in fatigue to check the shear capacity of the section between the slab and the girders; (2) Övik – A two span trough bridge strengthened with Near Surface Mounted Reinforcement (NSMR) of Carbon Fibre Reinforced Polymers (CFRP) tested in bending, shear and torsion; and (3) Kiruna – A five-span prestressed three girder bridge tested to shear-bending failures in the girders and in the slab.

    The failure capacities were considerably higher than what the code methods indicated. With calibrated and stepwise refined finite element models, it was possible to capture the real behaviour of the bridges. The experiences and methods may be useful in assessment and better use of other bridges.

  • 30. Nordin, Håkan
    et al.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Concrete beams strengthened with prestressed near surface mounted reinforcement (NSFR)2001In: FRP Composites in Civil Engineering: Proceedings of the International Conference on FRP Composites in Civil Engineering, Amsterdam: Elsevier, 2001, p. 1067-1075Conference paper (Refereed)
    Abstract [en]

    The need for repair and strengthening of concrete structures has increased considerably over the last decade. A number of methods for repair and/or strengthening of concrete structures have been used over the years, but very recently the use of carbon fiber reinforced polymer (CFRP) plate bonding has gained acceptance. The technique was originally developed with steel plates being bonded with an epoxy adhesive to a concrete structure, but lately advances have been made in use of more suitable plate materials such as CFRP composites. This paper presents a pilot study of lab tests for concrete beams strengthened with prestressed near surface mounted CFRP laminates. Primary results indicate an increased strengthening effect when the steel reinforcement yielded and an increased cracking load, but the ultimate load is the same as a beam strengthened without prestress. Failure modes were the same with or without prestress, failure in the fiber, but the prestressed beams had smaller deflections at failure.

  • 31.
    Puurula, Arto
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Savonia University of Applied Scinces, Kuopia, Finland.
    Enochsson, Ola
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Bodens kommun.
    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.
    Ohlsson, Ulf
    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
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Trafikverket.
    Paulsson, Björn
    Trafikverket.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Assessment of the Strengthening of an RC Railway Bridge with CFRP utilizing a Full-Scale Failure Test and Finite-Element Analysis2015In: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 141, no 1 (Special Issue), p. D4014008-1-D4014008-11, article id D4014008Article in journal (Refereed)
    Abstract [en]

    A finite element (FE) model was calibrated using the data obtained from a full-scale test to failure of a 50 year old reinforced concrete (RC) railway bridge. The model was then used to assess the effectiveness of various strengthening schemes to increase the loadcarrying capacity of the bridge. The bridge was a two-span continuous single-track trough bridge with a total length of 30 m, situated in Örnsköldsvik in northern Sweden. It was tested in situ as the bridge had been closed following the construction of a new section of the Railway line. The test was planned to evaluate and calibrate models to predict the load-carrying capacity of the bridge and assess the strengthening schemes originally developed by the European research project called Sustainable bridges. The objective of the test was to investigate shear failure, rather than bending failure for which good calibrated models are already available. To that end, the bridge was strengthened in flexure before the test using near-surface mounted square section carbon fiber reinforced polymer (CFRP) bars. The ultimate failure mechanism turned into an interesting combination of bending, shear, torsion, and bond failures at an applied load of 11.7 MN (2,630 kips). A computer model was developed using specialized software to represent the response of the bridge during the test. It was calibrated using data from the test and was then used to calculate the actual capacity of the bridge in terms of train loading using the current Swedish load model which specifies a 330 kN (74 kips) axle weight. These calculations show that the unstrengthened bridge could sustain a load 4.7 times greater than the current load requirements (which is over six times the original design loading), whilst the strengthened bridge could sustain a load 6.5 times greater than currently required. Comparisons are also made with calculations using codes from Canada, Europe, and the United States.

  • 32.
    Sabourova, Natalia
    et al.
    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.
    Puurula, Arto
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Enochsson, Ola
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    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
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Thun, Håkan
    The railway concrete arch bridge over Kalix river: dynamic properties and load carrying capacity2012In: Concrete Structures for Sustainable Community: proceedings of the International FIB Symposium 2012, Stockholm, Sweden, 11 - 14 June 2012 / [ed] Dirch H Bager; Johan Silfwerbrand, Stockholm: Swedish Concrete Association , 2012, p. 609-612Conference paper (Refereed)
  • 33.
    Sas, Gabriel
    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.
    Nilimaa, Jonny
    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.
    Bennitz, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Trafikverket.
    Strengthening of concrete structures with carbon fibre reinforced polymers (CFRP): case studies2012In: Concrete Structures for Sustainable Community: proceedings of the International FIB Symposium 2012, Stockholm, Sweden, 11 - 14 June 2012 / [ed] Dirch H. Bager; Johan Silfwerbrand, Stockholm: Swedish Concrete Association , 2012, p. 423-426Conference paper (Refereed)
    Abstract [en]

    Carbon Fibre Reinforced Polymers (CFRP) has found an increased application in strengthening of concrete structures. Mostly the CFRP is used as externally bonded reinforcement. However, prestressing of it gives a possibility to increase the capacity and stiffness of existing concrete structures. A number of tests in the laboratory as well as field case studies have been carried out. The paper describes some of them.

  • 34.
    Sas, Gabriel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Täljsten, Björn
    A model for predicting the shear bearing capacity of FRP-strengthened beams2008In: Mechanics of composite materials, ISSN 0191-5665, E-ISSN 1573-8922, Vol. 44, no 3, p. 245-256Article in journal (Refereed)
    Abstract [en]

    The shear failure of reinforced concrete beams needs more attention than the bending failure since no or only small warning precedes the failure. For this reason, it is of utmost importance to understand the shear bearing capacity and also to be able to undertake significant rehabilitation work if necessary. In this paper, a design model for the shear strengthening of concrete beams by using fiber-reinforced polymers (FRP) is presented, and the limitations of the truss model analogy are highlighted. The fracture mechanics approach is used in analyzing the bond behavior between the FRP composites and concrete. The fracture energy of concrete and the axial rigidity of the FRP are considered to be the most important parameters. The effective strain in the FRP when the debonding occurs is determined. The limitations of the anchorage length over the cross section are analyzed. A simple iterative design method for the shear debonding is finally proposed.

  • 35.
    Sas, Gabriel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Täljsten, Björn
    Barros, Joaquim
    University of Minho.
    Lima, Joao
    University of Minho.
    Arifovic, Fedja
    Technical University of Denmark.
    How reliable are the available models for predicting the FRP contribution for the shear resistance of RC beams?2008In: Proceedings of CCC 2008 - Challenges for Civil Construction / [ed] Torres Marques, FEUP edições (Faculdade de Engenharia da Universidade do Porto Edicoes), 2008Conference paper (Refereed)
    Abstract [en]

    The most well-known models for prediction of the contribution of externally bonded FRP for shear strengthening of reinforced concrete beams are compared on this paper. The comparison is based on experimental results from approximately 200 strengthened concrete beams with various strengthening configurations and geometric dimensions. The results are not promising and a large scatter between the considered models was obtained. In addition, none of these models predict the ultimate shear capacity very accurately, which is of serious concern considering that some of the models are used in various design codes.

  • 36.
    Sas, Gabriel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Demeter, Istvan
    Politechnica University of Timisoara.
    Nagy-György, Tamas
    Politechnica University of Timisoara.
    Stoian, Valeriu
    Politechnica University of Timisoara.
    Carolin, Anders
    Täljsten, Björn
    FRP strengthened RC panels with cut-out openings2008In: Proceedings of CCC 2008 - Challenges for Civil Construction / [ed] Torres Marques, FEUP edições (Faculdade de Engenharia da Universidade do Porto Edicoes), 2008Conference paper (Refereed)
    Abstract [en]

    A strengthening solution for multi-storey buildings in seismically active regions is considered. The Precast Reinforced Concrete Large Panel (PRCLP) structural system is described. Besides earthquakes, different problems during the last decades were identified in the PRCLP structural behaviour: design mistakes, neglected health monitoring, construction problems, change of use for example cut-out openings. The presented study is a part of an ongoing research program which deals with the influence of the Fibre Reinforced Polymer (FRP) strengthening on the behaviour of Precast RC Wall Panels (PRCWP) with cut out openings subjected to cyclic (seismic) and normal (gravity) loading. In this paper a brief literature survey concerning RC walls strengthened by FRP is presented and the experimental tests setup is discussed. The wall specimens were designed according to the 1981 Romanian code. Tests are described and a discussion based on previous experimental work on shear walls is undertaken and future research is suggested.

  • 37.
    Sas, Gabriel
    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.
    Barros, Joaquim
    University of Minho, School of Engineering, Department of Civil Engineering.
    Lima, Joao
    University of Minho, School of Engineering, Department of Civil Engineering.
    Carolin, Anders
    Are available models reliable for predicting the FRP contribution to the shear resistance of RC beams?2009In: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 13, no 6, p. 514-534Article in journal (Refereed)
    Abstract [en]

    In this paper the trustworthiness of the existing theory for predicting the fiber-reinforced plastic contribution to the shear resistance of reinforced concrete beams is discussed. The most well-known shear models for external bonded reinforcement are presented, commented on, and compared with an extensive experimental database. The database contains the results from more than 200 tests performed in different research institutions across the world. The results of the comparison are not very promising and the use of the additional principle in the actual shear design equations should be questioned. The large scatter between the predicted values of different models and experimental results is of real concern bearing in mind that some of the models are used in present design codes.

  • 38.
    Täljsten, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Aboudrar, Abderahim
    Burghauser, Andreas
    Carolin, Anders
    Fullskaleförsök på silor förstärkta med kolfiberväv2000Report (Other academic)
    Abstract [sv]

    Under sommaren 1999 utförde Stabilator AB i Samverkan med Odal Ek. förening och Luleå tekniska universitet, Testlab, förstärkning av fyra spannmålssilor med hjälp av utanpåliggande kolfiberväv. Denna teknik har vidareutvecklats vid Luleå tekniska universitet, avdelningen för Konstruktionsteknik. Kortfattat innebär förstärkningstekniken att armering i form av kolfiberväv limmas mot utsidan av en konstruktion. På så sätt bygger man upp en befintlig komposit på en existerande konstruktion. Metoden är flexibel och oftast mycket kostnadseffektiv. Två av de förstärkta anläggningarna var belägna i Västerås och två i Kvänum. I Kvänum förstärktes en silo på utsidan med remsor och en på insidan med heltäckande komposit. I Västerås förstärktes båda silorna på utsidan med remsor. Anledningen till förstärkning var att anläggningarna var underdimensionerade med avseende på tömningstrycket. Detta har medfört omfattande sprickbildning, korrosion samt i vissa snitt överskridande av armeringens flytgräns. I samband med förstärkningen applicerades töjningsgivare på såväl stålarmering och på den härdade kolfiberkompositen. Efter förstärking provades de förstärkta silorna genom att spannmål fylldes och tömdes i silorna. Registrering utfördes då av töjningar och belastning. Resultaten efter förstärkning var positivt och de befintliga armeringsjärnen avlastades väsentligt.

  • 39.
    Täljsten, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Carolin, Anders
    Mineral based bonding of CFRP to strengthen concrete structures2007In: Sustainable bridges: assessment for future traffic demands and longer lives / [ed] Jan Bien; Lennart Elfgren; Jan Olofsson, Wrocław: Dolnoslaskie Wydawnictwo Edukacyjne , 2007, p. 331-339Conference paper (Refereed)
    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 study with CFRP strengthened concrete beams. In this case the epoxy has been replaced with a mineral based composite (MBC). The results from the 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 The project was a part of the European funded research project Sustainable Bridges.

  • 40.
    Täljsten, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    CFRP - strengthening: concrete beams strengthened with near surface mounted CFRP laminates2001In: FRPRCS-5 :: fibre-reinforced plastics for reinforced concrete structures : proceedings of the Fifth International Conference on Fibre-Reinforced Plastics for Reinforced Concrete Structures, Cambridge, UK, 16-18 July 2001 / [ed] Chris Burgoyne, London: Thomas Telford Ltd , 2001, p. 107-116Conference paper (Refereed)
  • 41.
    Täljsten, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    CFRP strengthening of concrete beams: testing in sub-zero temperature2007In: International journal of materials & product technology, ISSN 0268-1900, E-ISSN 1741-5209, Vol. 28, no 1/2, p. 29-45Article in journal (Refereed)
    Abstract [en]

    Strengthening structures with epoxy bonded Carbon Fibre- Reinforced Polymer (CFRP) plates and sheets are today a well-known and over the world common used method to improve a structure performance. The composite materials used for strengthening are very light and easy to handle, have good durability and do not normally need to be maintained over time. However, disadvantages might be mechanical damage and long term properties. There is also a question regarding the behaviour of CFRP strengthen structures in cold climates, for example will the structure become more brittle during the winter compared to the summer period? In this paper the last issue will be addressed. CFRP strengthen concrete beams have been tested in sub-zero temperature and loaded up to failure. The cold climate tests are then compared with similar beams tested in room climate. From the tests no significant difference between the beams tested in sub-zero and room temperatures could be found.

  • 42.
    Täljsten, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Förstärkning av betongkonstruktioner med fiberarmerade kompositer: en överblick2006In: Bygg & Teknik, ISSN 0281-658X, no 7Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Betongkonstruktioner har normalt en lång livslängd och har bra prestanda, speciellt om underhållet sköts korrekt. Brister det i underhåll kan man behöva reparera konstruktionen till ursprunglig prestanda. I de fall prestanda behöver ökas kan uppgradering vara nödvändigt. Prestanda kan delas in i fyra olika delar, estetik, funktion, beständighet och bärförmåga. Faktorer som inverkar på estetiken kan gälla så enkla delar som klotter eller icke konstruktiva åtgärder som målning. Brister i funktion kan till exempel vara om en bro är i fullgott skick med avseende på beständighet, utseende och bärförmåga, men en breddning av befintlig väg medför att bron är för smal och av den orsaken behöver ersättas. Vilket i ytterlighetsfallet kan innebära att bron byts ut.

  • 43.
    Täljsten, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Near surface mounted reinforcement (NSMR) to strengthen concrete structures2007In: Sustainable bridges: assessment for future traffic demands and longer lives / [ed] Jan Bien; Lennart Elfgren; Jan Olofsson, Wrocław: Dolnoslaskie Wydawnictwo Edukacyjne , 2007, p. 341-354Conference paper (Refereed)
  • 44.
    Täljsten, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Strengthening of a concrete railway bridge in Luleå with carbon fibre reinforced polymers - CFRP: load bearing capacity before and after strengthening1999Report (Other academic)
    Abstract [en]

    The railroad between Gällivare and Luleå in the northern part of Sweden is called Malmbanan. Heavy loads of iron ore are transported on this railroad daily. During long time the weight of the load has been approximately 5 000 tons per train which correspond to 25 tons per axle. A wish from LKAB to increase the load up to 30 tons per axle or 6 000 tons per train exists. Calculations of the load bearing capacity of the bridges show that many of them will not be able to carry these higher loads without strengthening. There exist several methods for strengthening of a concrete structure. A strengthening method that have been more and more used during the last years is bonding of carbon fibre composite fabrics or laminates to the surface of the structure. The Swedish Rail Road authorities wanted to investigate the method more closely and of that reason a bridge were strengthened in Luleå during the summer of 1998. The bridge is built of concrete and has three spans. It is located at Kallkällan NW of the city centre. The objective of the test was not only to investigate the strengthening effect but also to study the work methods and the work environment during handling of the thermosetting plastic. Before the strengthening system was applied, the concrete surface was smoothened by sandblasting and grinding. Putty was used for bigger irregularities. The strengthening system consists of a hand lay up system with epoxy and unidirectional carbon fibre sheets. Later the concrete surface was coated by a polyurethane paint, with function to protect against UV-radiation and mechanical damage and also to give an increased aesthetic value. During the work the environmental and health aspects were taken into account and the epoxy, as well as the epoxy components were handled in a strict and careful manner, for example all the waste were placed in closed containers and sent to destruction. In the report, general equations, modes of action and design principles for strengthening by externally bonded fibre-reinforced polymers are described shortly. Some of the calculations that have been done for the bridge are also shown. For investigation of the strengthening system a comprehensive test program was undertaken on the bridge before and after the strengthening system was mounted. Both strains and deformations were measured when ore trains at different speeds passed on the bridge. The weight of each train was measured to be able to compare measurements of different trains with each other. Measured values from testing were relatively close to theoretical calculated levels, before and after the strengthening, both regarding strains and deformation. The measurement showed that the strengthening had increased the stiffness of the bridge by about 16%. Also measurements of the concrete quality were undertaken as well as an investigation of the bridge condition. The difficulties to decide the clamping of the slab in the load bearing beams and the chosen models for calculations have a big influence of the theoretical results. However, the measurements show that the method of strengthening concrete bridges by bonding carbon fibres to the surface works in an effective manner even when trains are frequenting the bridge during the strengthening work. In chapter 1 a short introduction and background to the project is given. In chapter 2 theoretical work are described and in chapter 3 the execution of the strengthening work is described. In chapter 4 the results and the performance from the measurements are recorded. In chapter 5 a comparison between theory and tests are made. In chapter 6 conclusions are presented and finally in chapter 7 proposal to further work is given.

  • 45.
    Täljsten, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Strengthening of concrete beams in shear: theory and test2001In: FRP Composites in Civil Engineering: Proceedings of the International Conference on FRP composites in Civil Engineering, Amsterdam: Elsevier, 2001, Vol. 1, p. 657-667Conference paper (Refereed)
    Abstract [en]

    The paper provides a summary of a theoretical derivation of equations for strengthening concrete beams in shear with CFRP (carbon fiber reinforced polymer) sheets and presents a limited number of laboratory tests. A fairly good agreement is obtained with a comparison between theory and testing. Still, additional tests will be necessary to verify and control the derived theory. The future tests should focus not only on the different angles of the fiber but also the number of layers and different stiffnesses of the fibers used. The aim of these tests is to find a factor for safety where the design equations can be used on the safe side without putting strong limitations on the strengthening system used.

  • 46.
    Täljsten, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Helmerich, Rosmarie
    Bundesanstalt für Materialforschung.
    Rehabilitation of railway bridges2007In: Sustainable bridges: assessment for future traffic demands and longer lives / [ed] Jan Bien; Lennart Elfgren; Jan Olofsson, Wrocław: Dolnoslaskie Wydawnictwo Edukacyjne , 2007, p. 303-312Conference paper (Refereed)
    Abstract [en]

    The presented work in work package 6 is a part of the European funded research project Sustainable Bridges. The objectives of this project are to: Increase the transport capacity of existing bridges by allowing axle loads up to 33 tons for freight traffic with moderate speeds or for speeds up to 350 km/hour for passenger traffic with low axle loads. Increase the mean residual service lives of existing bridges with up to 25 %. The project contains 9 work packages, where WP6 deals with new and innovative repair and strengthening methods for railway bridges. All work-packages are correlated. However in this paper the work carried out in work package 6 and how development of environmental friendly and non disturbing repair and strengthening methods may enhance management, strengthening and repair systems is presented.

  • 47.
    Täljsten, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Nordin, Håkan
    Concrete structures strengthened with near surface mounted reinforcement of CFRP2003In: Advances in Structural Engineering, ISSN 1369-4332, E-ISSN 2048-4011, Vol. 6, no 3, p. 201-213Article in journal (Refereed)
    Abstract [en]

    The need of maintenance, repair and upgrading of concrete structures has increased considerably over the last decade and will most likely continue to do so. There can be several reasons for this, but it can often be attributed to normal change of use, increased demands on the structure, errors in the design and/or construction phase or in the worst case, accidents. Different methods have been developed over the years for solving different rehabilitation problems. Recently, advanced composites used for external bonding in the form of fabrics or laminates have become an accepted method. Several thousands of objects around the world have been upgraded with advanced composites bonded to its surface. In most cases, this method is very competitive regarding both structural behaviour and economy, but there are also some drawbacks. The surface bonded composite material is relatively sensitive to fire, accidents or vandalism. In addition, the pre-treatment is relatively intensive and time consuming. However, if the composite material is placed in slots in the concrete cover some of these drawbacks can be overcome. This paper presents work carried out on near surface mounted reinforcement (NSMR) at Luleå University of Technology in Sweden.

  • 48.
    Täljsten, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Pedersen, Henning
    COWI A/S.
    Repair and strengthening of railway bridges: guideline2007In: Sustainable bridges: assessment for future traffic demands and longer lives / [ed] Jan Bien; Lennart Elfgren; Jan Olofsson, Wrocław: Dolnoslaskie Wydawnictwo Edukacyjne , 2007, p. 313-320Conference paper (Refereed)
    Abstract [en]

    This paper presents how a range of suitable strengthening method can be selected from the vast number of existing methods via a guideline. The guideline considers the structural system, type of problem and relevant circumstances. In the guideline, only methods that can be considered as new and investigated in the project Sustainable Bridges are at this moment introduced. However, the guideline can easily be updated with additional methods and systems following the same suggested approach. Furthermore, the guideline's precision in suggesting strengthening methods can be improved by use of future experience from real applications and development of different strengthening methods.

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