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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 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.

  • 4.
    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.

  • 5.
    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.

  • 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.
    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.

  • 7.
    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.

  • 8.
    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.

  • 9.
    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.

  • 10.
    Dăescu, Cosmin
    et al.
    Politechnica University of Timisoara.
    Nagy-György, Tamas
    Politechnica University of Timisoara.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Barros, Joaquim
    University of Minho.
    Popescu, Cosmin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Numerical Assessment of Dapped Beam Ends Retrofitted with FRP Composites2013In: FRPRCS-11: 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]

    This document presents the work related to the assessment of the effectiveness of strengthening reinforced concrete (RC) dapped-end beams using carbon fiber reinforced polymers (CFRP). Several non-linear finite element analyses were performed using different strengthening configurations, from the simplest solutions to the more complex ones in which different application schemes were overlapped. The work is focused on evaluating the strengthening systems, considering the ultimate capacities they can lead to and the failure modes involved. There were modeled 17 different strengthening configurations. While some of them provided a marginal in the ultimate load that can be applied, several of them provided important load bearing capacity increase. The observed failure modes ranged from a sudden failure of the whole strengthening system up to the desired progressive failure of the individual components of each strengthening system.

  • 11.
    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.

  • 12.
    Floruț, Sorin-Codruț
    et al.
    Politechnica University of Timisoara.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. NORUT, Department of Infrastructure Structures and Materials.
    Popescu, Cosmin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Stoian, Valeriu
    Tests on reinforced concrete slabs with cut-out openings strengthened with fibre-reinforced polymers2014In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 66, p. 484-493Article in journal (Refereed)
    Abstract [en]

    This paper presents the results of experimental investigations on reinforced concrete slabs strengthened using fibre-reinforced polymers (FRP). Eight tests were carried out on four two-way slabs, with and without cut-out openings. Investigations on slabs with cut-outs revealed that the FRP can be placed only around the edges of the cut-out when retrofitting the slabs whereas, in the situation of inserting cut-outs combined with increased demands of capacity, it is necessary to apply FRP components on most of the soffit of the slab. The proposed strengthening system enabled the load and deflection capacities of the FRP-strengthened slabs, in relation to their un-strengthened reference slabs, to be enhanced by up to 121% and 57% for slabs with and without cut-outs respectively.

  • 13.
    Gonzalez-Libreros, Jaime
    et al.
    Department of Civil, Environmental and Architectural Engineering, University of Padua.
    Sabau, Cristian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sneed, Lesley H.
    Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla .
    Sas, Gabriel
    Department of Infrastructure, Materials and Structural Engineering, Norut Narvik AS.
    Pellegrino, Carlo
    Department of Civil, Environmental and Architectural Engineering, University of Padua, .
    Effect of Confinement with FRCM Composites on Damaged Concrete Cylinders2017In: Strain-Hardening Cement-Based Composites: Shcc4 / [ed] Mechtcherine, Viktor; Slowik, Volker; Kabele, Petr, Dordrecht: Springer, 2017, p. 770-777Conference paper (Refereed)
    Abstract [en]

    Confinement of axially loaded concrete members in existing structures is required when a change in use is expected or when there is a need to upgrade the structure to meet current design standards. In addition, after unusual overloading events (e.g., earthquakes), axially loaded members can suffer damage that increases the need of their retrofitting by means of confinement. The study of fiber reinforced cementitious matrix (FRCM) composites for confinement of compression members has gained attention in recent years due to the capability to overcome some of the disadvantages associated with more traditional strengthening techniques. However, the available experimental evidence is still scarce, and research on the topic is necessary. In this paper, the results of an experimental campaign performed on concrete cylinders confined with FRCM jackets are presented. Before strengthening, some specimens were preloaded in order to achieve specified damage levels. The specimens were then subjected to uniaxial concentric compressive loading. The axial load and axial strain response was recorded for each specimen. In addition, the elastic modulus of confined and unconfined specimens was determined. Results show that confinement with FRCM composites is able to provide an increase in the axial capacity of undamaged and damaged concrete cylinders.

  • 14.
    Gonzalez-Libreros, Jaime
    et al.
    Department of Civil, Environmental and Architectural Engineering, University of Padua.
    Sabau, Cristian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sneed, Lesley
    Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology.
    Pellegrino, Carlo
    Department of Civil, Environmental and Architectural Engineering, University of Padua,.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Department of Infrastructure, Materials and Structural Engineering, NORUT.
    Experimental investigation on RC beams strenghened in shear with  externally bonded composites2016In: Eighth International Conference onFibre-Reinforced Polymer (FRP) Composites in Civil Engineering / [ed] J.G. Teng and J.G. Dai, Hong Kong, China: The Hong Kong Polytechnic University , 2016, p. 384-389Conference paper (Refereed)
    Abstract [en]

    This paper presents the results of an experimental campaign carried out to investigate the behavior of reinforcedconcrete (RC) beams strengthened in shear using externally bonded advanced composite materials. In order tocompare their performance, two different types of composite materials were used to strengthen the beams: fiberreinforced polymer (FRP) and fiber reinforced cementitious matrix (FRCM) composites. The beams were thentested in four-point bending scheme, and measurements regarding applied load and mid-span displacements wereacquired. Observations regarding the gain in shear strength, influence on mid-span deflection and ductility, andcomparison of the performance of the two strengthening systems are provided. For specimens strengthened withFRCM composite, the contribution to the shear strength provided by the FRCM strengthening system is comparedwith the value predicted by an analytical model found in the available literature.

  • 15.
    Gonzalez-Libreros, Jaime
    et al.
    Department of Civil, Environmental and Architectural Engineering, University of Padua.
    Sabau, Cristian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sneed, Lesley
    Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology.
    Pellegrino, Carlo
    Department of Civil, Environmental and Architectural Engineering, University of Padua,.
    Sas, Gabriel
    Department of Infrastructure, Materials and Structural Engineering, NORUT.
    Shear strengthening of RC beams with FRCM: what do we know so far?2016In: Eighth International Conference onFibre-Reinforced Polymer (FRP) Compositesin Civil Engineering / [ed] J.G. Teng and J.G. Dai, Hong Kong, China: The Hong Kong Polytechnic University , 2016, p. 462-467Conference paper (Refereed)
    Abstract [en]

    Shear failure of reinforced concrete (RC) beams is an undesirable mode of failure due to its sudden and brittlenature and thus needs to be carefully evaluated when planning a strengthening intervention. The use of fiberreinforced polymer (FRP) composites has shown to be capable of providing an adequate increase in shear strength.However, in recent years, there is interest in developing new techniques in which the positive attributes of FRPare utilized but some of its drawbacks are overcome. Among these techniques, fiber reinforced cementitious matrix(FRCM) composites, in which the organic resins are replaced by inorganic mortars, have shown promising results.In this paper, a bibliographical review of the available literature on FRCM shear strengthening of RC beams iscarried out. Two available design models are evaluated using a database compiled by the authors. The reviewshows that FRCM is able to provide an increase in strength and performance comparable to RC beams strengthenedwith FRP. However, the models are not able to accurately predict the behavior of FRCM strengthened beams.

  • 16.
    Gonzalez-Libreros, Jaime
    et al.
    Department of Civil, Environmental and Architectural Engineering, University of Padua.
    Sabau, Cristian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sneed, Lesley
    Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla .
    Pellegrino, Carlo
    Department of Civil, Environmental and Architectural Engineering, University of Padua, .
    Sas, Gabriel
    Department of Infrastructure, Materials and Structural Engineering, NORUT.
    State of research on shear strengthening of RC beams with FRCM composites2017In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 149, p. 444-458Article in journal (Refereed)
    Abstract [en]

    This paper summarizes the state of research on the topic of shear strengthening of RC beams using externally bonded FRCM composites. In the first part of this paper, a detailed bibliographical review of the literature on the shear strengthening of RC beams using FRCM composites is carried out, and a database of experimental tests is developed. Analysis of the database shows that FRCM composites are able to increase the shear strength of RC beams. The effectiveness of the strengthening system appears to be influenced by parameters including the wrapping configuration, matrix compressive strength relative to the concrete compressive strength, and axial rigidity of the fibers. Different failure modes have been reported, including fracture of the fibers, detachment of the FRCM jacket (with or without concrete attached), and slippage of the fibers through the mortar. A possible interaction between the internal transverse steel reinforcement and the FRCM system has also been observed. In the second part of this paper, four design models proposed to predict the contribution of the FRCM composite to the shear strength of RC beams are assessed using the database developed. Results show that the use of the properties of the FRCM composite in Models 3 and 4 instead of the fiber mechanical characteristics does not significantly increase the accuracy of the models. A simple formulation such as that proposed by Model 1, based on the bare fiber properties, is found to be more accurate for beams with or without composite detachment.

  • 17.
    Guadagnini, M.
    et al.
    University of Sheffield.
    Serbescu, A.
    University of Sheffield.
    Ceroni, F.
    University of Sannio.
    Palmieri, A.
    Ghent University.
    Matthvs, S.
    Ghent University.
    Czaderski, C.
    Laboratory EMPA, Dubendorf.
    Olia, S.
    Laboratory EMPA, Dubendorf.
    Bilotta, A.
    University of Naples.
    Niaro, E.
    University of Naples.
    Szabo, Z.
    University of Budapest.
    Balazs, G.
    University of Budapest.
    Mazzotti, C.
    University of Bologna.
    Barros, J.
    University of Minho.
    Costa, I.
    University of Minho.
    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.
    Tamuzs, V.
    University of Latvia.
    Bond of FRP strengthening systems for concrete structures: A Round Robin Test2012In: Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Management / [ed] Fabio Biondini; Dan M. Frangopol, Boca Raton: CRC Press, 2012, p. 1179-1186Conference paper (Refereed)
    Abstract [en]

    Although various test methods to examine the local bond behaviour of FRP strengthening systems to concrete have been proposed thus far, their implementation can lead to a wide range of results and a standard methodology has yet to be generally accepted. With these issues in mind, a Round Robin Testing (RRT) programme was carried out to assess the performance and reliability of small scale testing on various FRP strengthening systems, including both externally bonded laminates and near surface mounted reinforcement. Ten laboratories and eight manufacturers and suppliers participated in this extensive international exercise, which was initiated within the framework of the European funded Marie Curie Research Training Network, EN-CORE, with the support of Task Group 9.3 of the International Federation for Structural Concrete (fib). This paper describes the proposed testing programme and summarized some of the results obtained by the participating laboratories.

  • 18.
    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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    Nagy-György, Tamas
    et al.
    Politechnica University of Timisoara.
    Daescu, Cosmin
    Politechnica University of Timisoara.
    Diaconu, Dan
    Politechnica University of Timisoara.
    Stoian, Valeriu
    Politechnica University of Timisoara.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Dan, Daniel
    Prestressed concrete beam support zone strengthened with composites: Experimental results2007In: Proceedings of International Conference in Civil Engineering and Architecture - EPKO 2007, Miercurea Ciuc, Romania, 2007Conference paper (Refereed)
  • 22.
    Nagy-György, Tamas
    et al.
    Politechnica University of Timisoara.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Dăescu, Cosmin
    Politechnica University of Timisoara.
    Barros, Joaquim
    University of Minho.
    Stoian, V.
    Politechnica University of Timisoara.
    Experimental and numerical assessment of the effectiveness of FRP-based strengthening configurations for dapped-end RC beams2012In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 44, p. 291-303Article in journal (Refereed)
    Abstract [en]

    This paper presents experimental and numerical assessments of the effectiveness of strengthening dapped-end reinforced concrete beams using externally bonded carbon fiber reinforced polymers (CFRP). The research was prompted by a real application, in which the dapped-ends of several precast/prestressed concrete beams developed diagonal cracks due to errors during assembly. Hence, the dapped-ends were strengthened on-site using CFRP plates to limit further crack opening. In the empirical phase of the study, four similar specimens were tested: one unstrengthened reference specimen, two strengthened with high-strength CFRP plates, and one with high-modulus CFRP sheets. The specimens strengthened with plates had slightly higher load carrying capacity than the reference element, but failed by debonding, while the specimens strengthened with sheets showed no increase of capacity and failed by the fibers rupturing. Nonlinear finite element analysis of the specimens under the test conditions indicated that: a) debonding is more likely to occur at the inner end of dapped-ends, and b) the capacity could have been increased by up to 20% if the plates had been mechanically anchored.

  • 23.
    Nagy-György, Tamas
    et al.
    Politechnica University of Timisoara.
    Stoian, Valeriu
    Politechnica University of Timisoara.
    Dan, Daniel
    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.
    Diaconu, Dan
    Politechnica University of Timisoara.
    Mosoarca, Marius
    Politechnica University of Timisoara.
    Research results on RC walls and dapped beam ends strengthened with FRP composites2007In: Fibre-reinforced polymer reinforcement for concrete structures: proceedings of the 8th international symposium on fibre-reinforced polymer reinforcement for concrete structures ; Patras, Greece, July 16- 18, 2007 / [ed] Thanasis Triantafillou, Patras: FRPRCS-8 Symposium Secretariat , 2007Conference paper (Refereed)
  • 24.
    Nilimaa, Jonny
    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.
    Häggström, Jens
    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.
    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.
    More Realistic Codes for Existing Bridges2016In: IABSE CONGRESS, STOCKHOLM, 2016: Challenges in Design and Construction of an Innovativeand Sustainable Built Environment / [ed] Elfgren, Lennart; Jonsson, Johan; Karlsson, Mats; Rydberg-Forssbeck, Laja; Sigfrid, Britt, CH - 8093 Zürich, Switzerland, 2016, p. 399-407Conference paper (Refereed)
    Abstract [en]

    Examples are given from comparisons of analyses based on (1) code models, (2) finite element models and (3) full scale tests to failure of three bridges. The analyses based on the code models gave very conservative results, while the finite element models could better predict the real behaviour.

  • 25.
    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.

  • 26.
    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.

  • 27.
    Popescu, Cosmin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Dăescu, Cosmin
    Politechnica University of Timisoara.
    Tamás, Nagy-György
    Politechnica University of Timisoara.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Disturbed regions in dapped-end beams: numerical simulations of strengthening techniques2013In: Nordic Concrete Research, ISSN 0800-6377, Vol. 48, no 2, p. 14-26Article in journal (Refereed)
    Abstract [en]

    This paper investigates the effectiveness of strengthening reinforced concrete (RC) dapped-end beams using carbon fiber reinforced polymers (CFRP). Parametric studies are performed by means of numerical simulations in which several types of composite materials as well as their orientation are combined. The primary objectives of this research were the evaluation of the strengthening systems in terms of ultimate capacities and the failure modes involved. Results show that only some of them provide significant load bearing capacity increase. The observed failure modes ranged from a sudden failure up to the desired progressive failure of the strengthening system.

  • 28.
    Popescu, Cosmin
    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.
    The Development of an Experimental Program through Design of Experiments and FEM Analysis: A Preliminary Study2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 51, p. 29-42Article in journal (Refereed)
    Abstract [en]

    This paper presents an experimental test setup which allows investigation of the structural behaviour for axially loaded concrete walls with openings. The test matrix was developed with the help of design of experiments technique. A two level factorial experiment has been designed resulting in a total of nine wall specimens. Previous research has shown that the ultimate capacity of concrete walls is dependent on the boundary conditions. Therefore, a new test-rig was proposed and designed to work according to the imposed conditions. Nonlinear simulations calibrated on a previous experimental program were used to obtain the reaction forces.

  • 29.
    Popescu, Cosmin
    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. NORUT, Department of Infrastructure Structures and Materials.
    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.
    Concrete walls weakened by openings as compression members: A review2015In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 89, p. 172-190Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to review the advances that have been made in the design of monolithic and precast reinforced concrete walls, both with and without openings, subject to eccentrically applied axial loads. Using the results of previous experimental studies, a database was assembled to enable statistical assessment of the reliability of existing design models. Several design aspects are highlighted, including the size and position of openings, and the roles of boundary conditions and geometric characteristics. In addition, the performance of fiber-reinforced polymers in strengthening wall openings is discussed. Overall it is found that design codes provide more conservative results than alternative design models that have been proposed in recent studies. Research into the strengthening of walls with openings is still in its early stages, and further studies in this area are needed. The paper therefore concludes by highlighting some areas where new investigations could provide important insights into the structural behaviour of strengthened elements.

  • 30.
    Popescu, Cosmin
    et al.
    Northern Research Institute — NORUT.
    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.
    Concrete walls with cutout openings strengthened by FRP confinement2017In: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 21, no 3, article id 04016106Article in journal (Refereed)
    Abstract [en]

    Redesigning buildings to improve their space efficiency and allow changes in use is often essential during their service lives tocomply with shifts in living standards and functional demands. This may require the introduction of new openings in elements such as beams,walls, and slabs, which inevitably reduces their structural performance and hence requires repair or strengthening. However, there are uncertaintiesregarding both the effects of openings and the best remedial options for them. Here, the authors report on an experimental investigation ofthe effectiveness of fiber-reinforced polymer (FRP)–based strengthening for restoring the axial capacity of a solid RC wall after cutting openings.Nine half-scale specimens, designed to represent typical wall panels in residential buildings with and without door-type openings, were testedto failure. It was found that FRP-confinement and mechanical anchorages increased the axial capacity of walls with small and large openings(which had 25 and 50% reductions in cross-sectional area, respectively) by 34–50% and 13–27%, to 85–94.8% and 56.5–63.4% of their precuttingcapacity, respectively. 

  • 31.
    Popescu, Cosmin
    et al.
    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.
    Performance of RC Walls with Openings Strengthened by Fiber Reinforced Polymers: An Experimental and Theoretical Investigation2017In: Advances in Construction Materials and Systems: Proceedings of an International Conference (ICACMA), Chennai, India, September 3-8 2017 / [ed] Manu Santhanam; Ravindra Gettu; Radhakrishna G. Pillai; Sunitha K. Nayar, Paris-France: Rilem publications, 2017, Vol. 2, p. 509-517Conference paper (Refereed)
    Abstract [en]

    Redesigning buildings to improve their space efficiency and allow changes in use is  often essential during their service lives to comply with shifts in living standards and functional demands. This may require the introduction of new openings in elements e.g. walls, which inevitably reduces their structural performance, and hence necessitates repair or strengthening. Here the authors report an experimental investigation of the effectiveness of fibre-reinforced polymer (FRP)-based strengthening for restoring the axial capacity of a solid reinforced concrete wall after cutting openings. Nine half-scale specimens, designed to represent typical wall panels in residential buildings with and without door-type openings, were tested to failure. FRP-confinement and mechanical anchorages increased the axial capacity of walls with small and large openings (which had 25% and 50% reductions in cross-sectional area, respectively) by 34-50% and 13-27%, to 85-94.8% and 56.5-63.4% of their pre-cutting capacity, respectively. Current design models are assessed against experimentally obtained capacities.

  • 32.
    Popescu, Cosmin
    et al.
    Northern Research Institute - NORUT.
    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.
    Two-way walls with cut-out openings strengthened by fiberreinforced polymers2016In: 19th IABSE Congress Strockholm 21-23 September 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment / [ed] Lennart Elfgren, Johan Jonsson, Mats Karlsson, Lahja Rydberg-Forssbeck and Britt Sigfrid, CH - 8093 Zürich, Switzerland: International Association for Bridge and Structural Engineering, 2016, p. 1394-1400Conference paper (Refereed)
    Abstract [en]

    In refurbishment projects structural modifications may be required such as the addition of new openings. These openings are a source of weakness and can reduce the structures' stiffness and load-bearing capacity. As a result repairing may be necessary to restore their initial performances. The paper presents results of an experimental program performed to investigate the effectiveness of FRP-based strengthening for restoring the axial capacity of a solid reinforced concrete wall after cutting door openings. Nine half scale concrete walls with and without cut-out openings subjected to a uniformly distributed axial load with a small eccentricity were tested to failure. Increases in axial strength, ductility, steel reinforcement and FRP strain utilization were measured and presented in this paper. The application of the FRP confinement increases the capacity and the stiffness of the specimens with cut-out openings. The axial strengths were between 85-94.8% and 56.5-63.4% for specimens having a small and large opening, respectively, of that of a solid wall.

  • 33.
    Popescu, Cosmin
    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.
    Sabau, Cristian
    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.
    Effect of cut-out openings on the axial strength of concrete walls2016In: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 142, no 11, article id 4016100Article in journal (Refereed)
    Abstract [en]

    Old structures are frequently modified to comply with current living standards and/or legislation. Such modifications may include the addition of new windows or doors and paths for ventilation and heating systems, all of which require openings to be cut into structural walls. However, effects of the required openings are not sufficiently understood. Thus, the objective of the work reported here was to analyze openings’ effects on the axial strength of large concrete wall panels. Three half-scaled walls with two opening configurations, corresponding to “small” and “large” door openings, were subjected to a uniformly distributed axial load with a small eccentricity. The results indicate that the 25% and 50% reductions in cross-sectional area of the solid wall caused by introducing the small and large openings reduced the load-carrying capacity by nearly 36% and 50%, respectively. The failure progression was captured using digital image correlation technique and the results indicated involvement of a plate mechanism rather than uniaxial behavior as adopted in current design codes. Using a simplified procedure, the load-carrying capacity was predicted using existing design models found in the research literature and design codes.

  • 34.
    Popescu, Cosmin
    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.
    Sabau, Cristian
    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.
    Experimental tests on RC walls with openings strengthened by FRP2015In: The 12th International Symposium on Fiber Reinforced Polymers for Reinforced Concrete Structures (FRPRCS-12) & The 5th Asia-Pacific Conference on Fiber Reinforced Polymers in Structures (APFIS-2015) / [ed] Zhishen Wu; Gang Wu; Xin Wang, Nanjing, China: Southeast University , 2015Conference paper (Refereed)
    Abstract [en]

    Functional modifications of the old structures are common because existing structures must often be adapted to comply with current living standards. Such modifications may include the addition of new windows or doors and paths for ventilation and heating systems, all of which require openings to be cut into structural walls. The purpose of this experimental program is to investigate the behaviour of two-way RC walls with openings and strengthened by FRP. Nine half scale RC walls with two opening configurations, i.e. small and large door opening, were subjected to a uniformly distributed axial load with a small eccentricity. The paper presents the results of the experimental programme such as the ultimate capacity and deflection profiles. Moreover, the influence of the opening and the strengthening contribution to the overall capacity was also assessed and presented in this paper.

  • 35.
    Popescu, Cosmin
    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.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    A state of the art review on walls with openings strengthened by use of fiber reinforced polymers2014In: Proceedings of The 7th International Conference on FRP Composites in Civil Engineering (CICE 2014) / [ed] Raafat El-Hacha, Vancouver, British Columbia, Canada: International Institute for FRP in Construction (IIFC) , 2014, article id 128Conference paper (Refereed)
    Abstract [en]

    The purpose of this paper is to review the advances made in designing of monolithic and precast reinforced concrete (RC) walls with openings subjected to axial and eccentric loads. Nowadays, functionality and modifications of the structures are often encountered. Therefore, openings such as new windows, doors or paths for ventilations are highly demanded for RC walls. Based on previous studies, a critical review of the experimental and theoretical aspects of walls with openings and then retrofitted by use of fiber reinforced polymers (FRPs) are also presented. The simplified method provided by design codes fails in recognizing any contribution to the wall strength of the steel reinforcement or in some cases for the effect of side restraints. The presence of a new opening will decrease the axial capacity, thus, requiring upgrading. Satisfactory results were found when FRP was placed in the vicinity of the openings, being capable to restore the initial capacity. However, despite the considerable research carried out, there are still important research gaps that need to be further investigated.

  • 36.
    Popescu, Cosmin
    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.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Experimental Program for Axially Loaded RC Walls with Openings Strengthened by FRP2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 285-288Article in journal (Refereed)
    Abstract [en]

    The presence of a new opening will decrease the axial capacity, thus, requiring upgrading. Satisfactory results were found when FRP was placed in the vicinity of the openings, being capable to restore the initial structural capacity. However, despite the considerable research carried out, there are still important research gaps that need to be further investigated. In this paper an experimental program aimed to study the influence of opening size and the strengthening pattern for RC walls will be presented. To achieve this aim, a two-level factorial experiment has been designed resulting in a total of nine wall specimens.

  • 37.
    Popescu, Cosmin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Schmidt, Jacob W.
    Department of Civil Engineering, Technical University of Denmark, Technical University of Denmark, Division of Structural Engineering.
    Goltermann, Per
    Technical University of Denmark, Division of Structural Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Assessment of RC walls with cut-out openings strengthened by FRP composites using a rigid-plastic approach2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 150, p. 585-598Article in journal (Refereed)
    Abstract [en]

    Building refurbishment works frequently require the cutting of new openings in concrete walls. Cutting new openings weakens the overall response of such elements, so they usually require strengthening. However, current design codes offer little guidance on strengthening walls with openings, and less still on the use of non-metallic reinforcements such as FRP (Fibre Reinforced Polymers) to ensure sufficient load bearing capacity. This paper proposes a new procedure based on limit analysis theory for evaluating the ultimate load of walls with cut-out openings that have been strengthened with carbon-FRP (CFRP). First, the approach is verified against transverse (out-of-plane) and axial (in-plane) loading for unstrengthened specimens. These loading types result in different failure mechanisms: transverse loading leads to failure due to yielding/rupture of the steel reinforcement while axial loading leads to failure by concrete crushing. Second, the proposed method is further developed for CFRP-strengthened specimens under axial loading. It accounts for the contribution of CFRP indirectly, by updating the concrete model with an enhanced compressive strength as a result of confining the piers. Predictions made using the new method agree closely with experimental results.

  • 38.
    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.

  • 39.
    Puurula, Arto
    et al.
    Savonia University of Applied Sciences, Kuopia, Finland.
    Enochsson, Ola
    Bodens kommun, Sverige.
    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.
    Ohlsson, Ulf
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    3D non-linear FE analysis of a full scale test to failure of a RC Railway Bridge strengthened with carbon fibre bars2016In: 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: International Association for Bridge and Structural Engineering, 2016, p. 2527-2535Conference paper (Refereed)
    Abstract [en]

    At a full scale loading test to failure a 50 year old concrete railway trough bridge in Örnsköldsvik, in northern Sweden was tested to failure. The test was a part of the European Research Project “Sustainable Bridges” regarding assessment and strengthening of existing bridges. In the projectnew calculation methods were developed to capture the behaviour of the bridge during increasing load. The bridge was strengthened in bending with rods of Carbon Fiber Reinforced Polymer (CFRP) before the loading test. Failure was reached for an applied load of 11.7 MN by pulling a steel beam placed in the middle of one of the two spans downwards. The achieved failure was a combination of bond, shear, torsion and bending. The developed model, a 3D -non-linear finiteelement (FE) model with discrete reinforcement, gave accurate accounts of the response of thebridge. The FE calculations show the effect of the strengthening with CFRP and even the effect of the epoxy when using the Near Surface Mounted Reinforcement (NSMR) strengthening method.

  • 40.
    Puurula, Arto
    et al.
    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.
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Loading to failure and 3D nonlinear FE modelling of a strengthened RC bridge.2014In: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 10, no 12, p. 1606-1619Article in journal (Refereed)
    Abstract [en]

    A reinforced concrete railway trough bridge in Örnsköldsvik, Sweden, was strengthened in bending with rods of carbon-fibre-reinforced polymer and loaded to failure. The aim was to test and calibrate methods developed in the European Research Project ‘Sustainable Bridges’ regarding assessment and strengthening of existing bridges. A steel beam was placed in the middle of one of the two spans and was pulled downwards. Failure was reached at an applied load of 11.7 MN. It was initiated by a bond failure caused by a combined action of shear, torsion as well as bending after yielding in the longitudinal steel reinforcement and the stirrups. The bond failure led to a redistribution of the internal forces from the tensile reinforcement to the stirrups, causing the final failure. The computer models developed to simulate the loading process were improved step by step from linear shell models to more detailed models. The most developed model, a three-dimensional nonlinear finite element model with discrete reinforcement, gave accurate accounts of the response of the bridge.

  • 41.
    Puurula, Arto
    et al.
    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.
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Load carrying capacity of a RC Bridge in Örnsköldsvik, Sweden2011In: Nordic Concrete Research: Proceedings of the XXI Nordic Concrete Research Symposium, Hämeenlinna, Finland 2011, Oslo: The Nordic Concrete Federation , 2011, p. 29-32Conference paper (Refereed)
  • 42.
    Qin, Xiao-Chuan
    et al.
    School of Civil Engineering, Southeast University.
    Ming, Shao-Ping
    School of Civil Engineering, Southeast University.
    Cao, Da-Fu
    School of Civil Science and Engineering, Yangzhou University.
    Tu, Yong-Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Grip, Niklas
    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.
    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.
    Evaluation of freeze-thaw damage on concrete material and prestressed concrete specimens2016In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 125, p. 892-904Article in journal (Refereed)
    Abstract [en]

    The pore structure of the hardened concrete and the microscopic changes of a few selected pores throughout the freeze-thaw test were investigated by a method combining RapidAir and digital metalloscope. Traditional tests were also performed to evaluate the macroscopic change caused by freeze-thaw cycles (FTCs). The investigation shows that the concrete material, of which the spacing factor is 0.405 mm and the air content is 2.38%, can still withstand more than 300 FTCs. Severe microscopic damages occurred after approximately 200 FTCs and the freeze-thaw damage were gradually aggravated afterwards. Prestress forces have a remarkable impact on the failure pattern under FTCs. It was further found that the compressive strength as an indicator is more reliable than the relative dynamic modulus of elasticity in evaluating the freeze-thaw damage on concrete material. In addition, the test and analysis show that the measured prestress losses of bonded specimen are larger than that of unbounded specimen under the attack of FTCs due to the duct grouting effect. The ultimate freeze-thaw prestress loss is about 5% of σconσcon for both the bonded and unbonded specimens because the grouting cement paste will eventually be completely destroyed.

  • 43.
    Sabau, Cristian
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Gonzalez-Libreros, Jaime
    Department of Civil, Environmental and Architectural Engineering, University of Padua.
    Sneed, Lesley
    Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology.
    Sas, Gabriel
    Department of Infrastructure, Materials and Structural Engineering, NORUT,.
    Pellegrino, Carlo
    Department of Civil, Environmental and Architectural Engineering, University of Padua,.
    Influence of the fiber type and matrix age of the bonding of FRCM composite strips applied to concrete substrates2016In: Eighth International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering / [ed] J.G. Teng and J.G. Dai, 2016, p. 456-461Conference paper (Refereed)
    Abstract [en]

    Fiber reinforced cementitious matrix (FRCM) composites represent an alternative to fiber reinforced polymer(FRP) composites for strengthening existing civil structures. FRCM is comprised of fibers, usually in the form ofa textile with an open-mesh configuration, embedded in an inorganic mortar matrix. It shares the advantages ofFRP systems and overcomes some of its drawbacks, which makes it suitable for a wide range of applications.Although research on this topic is still scarce, it has been shown that debonding represents a key factor in itsperformance. In order to gain more insight in this issue, a series of classical push-pull single-lap direct shear testswere carried out on basalt, carbon, and glass FRCM-concrete joints. The results allow for comparing theperformance of the joints with carbon, basalt, and glass fibers in terms of applied load – global slip response andfailure mode. The influence of matrix age was also investigated. The curing time of the mortar matrix was foundto influence the load carrying capacity of carbon FRCM – concrete joints.

  • 44.
    Sabau, Cristian
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez-Libreros, Jaime
    Department of Civil, Environmental and Architectural Engineering, University of Padua.
    Sneed, Lesley
    Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla .
    Sas, Gabriel
    Department of Infrastructure, Materials and Structural Engineering, NORUT, .
    Pellegrino, Carlo
    Department of Civil, Environmental and Architectural Engineering, University of Padua, .
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Use of image correlation system to study the bond behavior of FRCM-concrete joints2017In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 50, no 3, article id 172Article in journal (Refereed)
    Abstract [en]

    This paper presents a non-contact measurement approach, based on digital photogrammetry,applied to the experimental study of the bond behavior of fiber reinforced cementitious matrixcomposite (FRCM) - concrete joints tested in single-lap direct shear tests. The use of digitalphotogrammetry techniques and traditional contact measurement approaches for determiningdisplacement and strain are investigated and compared. The results show that measurements ofstrain in the fiber bundles determined using the image correlation system (ICS) correlate well withthose obtained from electrical strain gauges. However, differences of 38% to 52% were observedbetween the maximum strain measured with either ICS or electrical strain gages attached to thefiber bundles and the maximum strain in the fiber bundles computed from the maximum appliedload. ICS is also used to measure slip and strain of bare fiber bundles, and results show that theload distribution among fiber bundles is non-uniform. The proposed measurement approach showshigher spatial measurement resolution and increased accuracy compared to traditional contactapproaches by enabling measurements in each fiber bundle and overcoming the need to attachadditional elements to the tested specimen.

  • 45.
    Sabau, Cristian
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Popescu, Cosmin
    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.
    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.
    Local and global behavior of walls with cut-out openings in multi-story reinforced concrete buildingsIn: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Article in journal (Refereed)
    Abstract [en]

    This paper presents the finite element analysis (FEA) results of a multi-story reinforced concrete (RC) building having precast and cast-in-place load bearing walls. Door-type cut-out openings (height: 2.1 m, width: 0.9–4.4 m) were created at the first and second story of the building. Results from experimental tests on axially loaded RC panels were used to verify the modeling approach. The influence of cut-out openings on the response of individual RC panels, failure modes, and load redistribution to adjacent members was analyzed. Moreover, the wall bearing capacities obtained from FEA were compared with the values calculated from design equations. The results revealed that the robustness of multi-story buildings having RC load bearing wall systems decrease considerably with the creation of cut-out openings. However, owing to the initial robustness of the buildings, large cut-outopenings could be created under normal service conditions without strengthening of the building structure. Furthermore, design equations provided very conservative predictions of the ultimate capacity characterizing the solid walls and walls with small openings, whereas similar FEA and analytically predicted capacities were obtained for walls with large openings.

  • 46.
    Sabau, Cristian
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Popescu, Cosmin
    Northern Research Institute, Narvik, Norway.
    Sas, Gabriel
    Northern Research Institute, Narvik, Norway.
    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.
    Axially Loaded RC Walls with Cutout Openings Strengthened with FRCM Composites2018In: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 22, no 6, p. 04018046-1-04018046-16, article id 04018046Article in journal (Refereed)
    Abstract [en]

    Upgrading existing buildings to new functional requirements may require new openings that can weaken the structure, promptingthe need for strengthening. In such cases traditional strengthening solutions, such as creating a reinforced concrete (RC) or steel frame aroundthe opening, imply long-term restrictions in the use of the structure compared to solutions that use externally bonded composites. Two fabricreinforcedcementitious matrix (FRCM) composites were used in this study to restore the capacity of panels with newly created doortype openings to that of a solid panel. Five half-scale RC panels acting as two-way action compression members were tested to failure.Two full-field optical deformation measurement systems were used to monitor and analyze the global structural response of each testedpanel (i.e., crack pattern, failure mechanism, and displacement/strain fields). The performance of existing design methods for RC panelshas been assessed in comparison with the experimental results. The capacity of strengthened panels with small openings (450 × 1,050 mm) was entirely restored to that of the solid panel. However, for panels with large openings (900 × 1,050 mm), only 75% of the solid panel’scapacity was restored. The capacity of the strengthened panels was about 175 and 150% higher compared to that of reference panels withsmall and large openings, respectively.

  • 47.
    Sabau, Cristian
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Popescu, Cosmin
    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.
    Concrete Walls with Openings Strengthened Using FRCM Composites2017In: Advanced Composites in Construction: Conference Proceedings / [ed] Maurizio Guadagnini & Sue Keighley, Chesterfield: NetComposites Limited , 2017, p. 188-192Conference paper (Refereed)
    Abstract [en]

    In the current social and economic context, upgrading or retrofitting of existing buildings, instead of replacingwith new constructions, is becoming more and more popular due to shorter service interruptions,accessibility, and economic reasons. Upgrading building to current living standards and new functionalityneed often require new openings to be created in structural elements such as reinforced concrete walls andslabs. With the aim of improving existing strengthening solutions for such cases, this study presents someaspects of an experimental investigation of the effectiveness of fibre reinforced cementitious matrixcomposites (FRCM) strengthening for restoring the axial capacity of a solid reinforced concrete wall aftercreating new door openings. Five half-scale specimens, designed to represent typical wall panels inresidential buildings with and without door-type openings, were tested to failure. It was found that FRCMsystems were able to fully restore the axial capacity of the walls with small openings to that of the solid wall,and to restore the axial capacity of walls with large openings to approximately 75% of that of the solid wall.

  • 48.
    Sabau, Cristian
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Popescu, Cosmin
    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.
    Monitoring structural behavior of reinforced concrete walls with openings using digital image correlation2016In: IABSE CONGRESS, STOCKHOLM, 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment / [ed] ennart Elfgren, Johan Jonsson, Mats Karlsson, Lahja Rydberg-Forssbeck and Britt Sigfrid, CH - 8093 Zürich, Switzerland: International Association for Bridge and Structural Engineering, 2016, p. 1803-1811Conference paper (Refereed)
    Abstract [en]

    Several measuring techniques based on digital image correlation (DIC) are nowadays used in many fields. DIC measurements can facilitate documentation of crack patterns on specimens subject to loading, valuable information, which would otherwise be hard to obtain, especially in the case of reinforced concrete elements. This can not only give a better insight into the failure mechanism of the element, but also evaluate cracking as measure of serviceability.This article discusses existing serviceability limits and failure modes of reinforced concrete walls in buildings in light of results obtained using DIC on two half-scale reinforced concrete walls with openings tested to failure. Results suggest that cracks induced by a load level equivalent to 70% of ultimate load bearing capacity, do not exceed limits indicated in relevant guidelines.The failure mode of two way walls with openings was found to be similar to that of two way slabs with openings, however differences were identified in the development of the failure mechanism. Finally, two strengthening strategies of reinforced concrete walls are discussed.

  • 49.
    Sabau, Cristian
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Popescu, Cosmin
    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.
    Review of FRCM strengthening solutions for structural wall panelsIn: American Concrete Institute. Publication SP, ISSN 0193-2527, E-ISSN 1094-8120Article in journal (Refereed)
    Abstract [en]

    This paper summarizes the state-of-the-art on the topic of structural wall panels strengthened using fabric reinforced cementitious matrix composites (FRCM) composites. A systematic review of the literature is carried out to identify gaps in the available literature. A database of experimental tests, relevant for structural panels, was created and used to assess the influence of parameters such as test method, fiber type and material compressive strength, on the performance of FRCM strengthening. Since experimental investigations on walls strengthened with FRCM composites is still limited and mostly focused on shear, further investigations on walls as compression members can be considered timely, especially walls with openings, which have been overlooked. Experimental tests performed by the authors on reinforced concrete walls with openings are presented and assessed relative to the complete database. It was shown that FRCM composites are suitable repair solutions when new openings need to be created in existing walls.

  • 50.
    Sabau, Cristian
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Popescu, Cosmin
    Northern Research Institute – NORUT.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Schmidt, Jacob W.
    echnical University of Denmark, Department of Civil 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.
    Strengthening of RC beams using bottom and side NSM reinforcement2018In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 149, p. 82-91Article in journal (Refereed)
    Abstract [en]

    The allowable strain in fibre reinforced polymers reinforcement is limited by design codes to avoid debonding. The near-surface mounted (NSM) reinforcement technique has been proven to produce better anchorage behaviour compared to externally bonded reinforcement solutions. However, NSM solutions do not always eliminate debonding issues, with concrete cover detachment (CCD) typically occurring in RC beams strengthened for flexure. This experimental study investigated the efficiency of side mounted (S) compared to bottom mounted (B) NSM bars to prevent CCD. The experimental results were compared to models available in the literature that predict the observed failure modes and the crack spacing in the NSM anchorage zone. Compared to B-NSM, the S-NSM solution was successful in avoiding brittle CCD failure and showed increased rotational capacity and energy dissipation at failure. Existing CCD debonding models were found to be conservative.

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