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  • 1.
    Elfving, Carl
    et al.
    Totalförsvarets forskningsinstitut.
    Magnusson, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Modell för klassificering och värdering av skyddsobjekt2001Report (Other academic)
  • 2.
    Forsén, Rickard
    et al.
    Totalförsvarets forskningsinstitut.
    Magnusson, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Flyttbara skydd mot vapenverkan: en litteraturstudie2005Report (Other academic)
  • 3.
    Hartman, Mats
    et al.
    Totalförsvarets forskningsinstitut.
    Nilsson, Martin
    Totalförsvarets forskningsinstitut.
    Magnusson, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Forsén, Richard
    Totalförsvarets forskningsinstitut.
    Berglund, Roger
    Totalförsvarets forskningsinstitut.
    Sårbarhetsvärdering av camper: Förstudie2008Report (Other academic)
  • 4.
    Lidén, Ewa
    et al.
    Totalförsvarets forskningsinstitut.
    Magnusson, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Carlberg, Anders
    Totalförsvarets forskningsinstitut.
    Finkaliber mot betong och naturmaterial: Sammanställning av skjutförsök2007Report (Other academic)
  • 5.
    Magnusson, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Fibre reinforced concrete beams subjected to air blast loading2006In: Nordic Concrete Research, ISSN 0800-6377, no 35, p. 18-34Article in journal (Refereed)
    Abstract [en]

    This paper involves testing of steel fibre reinforced concrete(SFRC) beams subjected to static and dynamic loads. Thedynamic load was generated by a detonating explosive charge.The work focused upon studying the mechanical behaviour ofthe beams. The concrete compressive strength varied between36 MPa and 189 MPa with a fibre content of 1.0 percent byvolume. Two different fibre lengths having constant length-todiameterratio were employed. The experimental results indicatethat the toughness is reduced when increasing the compressivestrength and the dynamic strength is higher than thecorresponding static strength.

  • 6.
    Magnusson, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. Fortifikationsverket.
    Shear in Concrete Structural Elements Subjected to Dynamic Loads2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Concrete structural elements subjected to severe dynamic loads such as explosions at close range may cause shear failures. In the Oklahoma City bombing in 1995 two concrete columns on the ground level were reported to have failed in shear. Such shear failures have also been reported to occur in several experimental investigations when concrete beams and slabs were subjected to blast or impact loads. The dynamic shear mechanisms are not yet fully understood and it is therefore of research significance to further investigate these mechanisms. The main objective of the research presented in this thesis is to experimentally and theoretically analyse shear failures of reinforced concrete elements subjected to uniformly distributed dynamic loads.

    The experimental work consisted of concrete beams of varying concrete grades and reinforcement configurations subjected to blast loads. One series involved testing of steel fibre reinforced concrete (SFRC) beams and the other series involved tests with concrete beams reinforced with steel bars. The former investigation showed that SFRC beams can resist certain blast loads. In the latter investigation, certain beams subjected to blast loads were observed to fail in flexural shear while the same beams exhibited flexural failures in the static tests. Such shear failures specifically occurred in beams with relatively high reinforcement contents. With these experiments as reference, numerical simulations with Ansys Autodyn were performed that demonstrated the ability to predict flexural shear failures.

    A direct shear failure mode has also been observed in experiments involving concrete roofs subjected to intense distributed blast loads. In several cases, the roof slabs were completely severed from their supporting walls along vertical or near-vertical failure planes soon after the load had been applied. Theoretical analyses of the initial structural response of beams subjected to distributed loads were conducted with the use of Euler-Bernoulli beam theory and numerical simulations in Abaqus/Explicit. These analyses show that the initial structural response consists of shear stresses and bending moments developing at the supports. The remaining parts of the beam will be subjected to a rigid body motion. Further simulations with Abaqus shows that that dynamic direct shear failure appears to be due to a deep beam response with crushing of the compressive struts at the supports, and therefore differs from a static direct shear mode. The results also showed that parameters such as element depth, amount of reinforcement, load level and load duration played a role in developing a dynamic direct shear failure.

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  • 7.
    Magnusson, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Structural concrete elements subjected to air blast loading2007Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In the design of structures to resist the effects of air blast loading or other severe dynamic loads it is vital to have large energy absorbing capabilities, and structural elements with large plastic deformation capacities are therefore desirable. Structures need to be designed for ductile response in order to prevent partial or total collapse due to locally failed elements. The research in this thesis considers experimental and theoretical studies on concrete beams of varying concrete strength. The nominal concrete compressive strength varied between 30 MPa and 200 MPa. A total of 89 beams were tested of which 49 beams were reinforced with varying amounts of tensile reinforcement. These beams were also reinforced with stirrups and steel fibres were added to a few beams. The remaining 40 beams were only reinforced with steel fibres with a fibre content of 1.0 percent by volume. Two different fibre lengths having constant length-to-diameter ratio were employed. The tests consisted of both static and air blast tests on simply supported beams. The blast tests were performed within a shock tube with a detonating explosive charge. All experimental research focused on deflection events, failure modes and loads transferred to the supports. The dynamic analyses involve single-degree-of-freedom (SDOF) modelling of the beam response and the use of iso-damage curves. Also, the dynamic support reactions were calculated and compared with test results.

    For beams with tensile reinforcement, the failure mode of some beam types was observed to change from a flexural failure in the static tests to a flexural shear failure in the dynamic tests. Beams with a high ratio of reinforcement and not containing steel fibres failed in shear, whereas beams with a lower ratio of reinforcement failed in flexure. The introduction of steel fibres prevented shear cracks to develop, thus increasing the shear strength of the beams. The presence of steel fibres also increased the ductility and the residual load capacity of the beams. Beams subjected to air blast loading obtained an increased load capacity when compared to the corresponding beams subjected to static loading. The SDOF analyses showed good agreement with the experimental results regardless of concrete strength and reinforcement amount. The results of using iso-damage curves indicate conservative results with larger load capacities of the beams than expected. The theoretical evaluations of the dynamic reactions were in agreement with the measured average reactions, both in amplitudes and in general shape.

    The experimental results with steel fibre reinforced concrete beams indicate that the dynamic strength was higher than the corresponding static strength and that the toughness was reduced when increasing the compressive strength. Beams of normal strength concrete failed by fibre pull-out while a few beams of high strength concrete partly failed by fibre ruptures. It may be favourable to use shorter fibres with smaller aspect ratios in structural elements of high strength concrete and subjected to large dynamic loads.

    Further research should involve studies on the size effect, on different boundary conditions, on different types of structural elements and on the combination of blast and fragment loads. The theoretical work should involve analyses both with the use of SDOF modelling and finite element analysis.

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  • 8.
    Magnusson, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Hansson, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Air-blast-loaded, high-strength concrete beams. Part II: Numerical non-linear analysis2010In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 62, no 4, p. 235-242Article in journal (Refereed)
    Abstract [en]

    The results from this investigation demonstrate the ability to perform numerical simulations of dynamic structural response of concrete elements subjected to air blast loading. Beams of both high-strength concrete (HSC) and normal-strength concrete (NSC) were studied. Also beams with two concrete layers of different strength were simulated. It is of particular interest to investigate the use of material models for implementation with software for the explicit analysis of non-linear dynamic events. The influences of concrete strength, amounts of reinforcement, the bond between concrete and reinforcement, bi-linear strain softening of concrete, the strain rate dependence of reinforcement and boundary conditions at the supports were studied. The simulations were performed with the text data as reference through comparison between numerical examples and experimental test results. It was possible numerically to analyse the dynamic behaviour of beams tested in situ and to describe the observed failure modes of these beams. The analysis tool will be used for evaluating the dynamic strength of future protective structures of HSC, possibly with parts consisting of NSC elements.

  • 9.
    Magnusson, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Hallgren, Mikael
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    High performance concrete beams subjected to shock waves from air blast, part 22003Report (Other academic)
  • 10. Magnusson, Johan
    et al.
    Hallgren, Mikael
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    High strength concrete beams subjected to shock waves from air blast2002In: Proceedings of the 6th International Symposium on Utilization of high strength/high Performance Concrete, p. 355-368Article in journal (Refereed)
  • 11.
    Magnusson, Johan
    et al.
    Swedish Defence Research Agency, FOI.
    Hallgren, Mikael
    Scandiaconsult.
    Reinforced high strength concrete beams subjected to air blast loading2004In: STRUCTURES UNDER SHOCK AND IMPACT VIII, ASHURST, ENGLAND: WIT PRESS , 2004, p. 53-62Conference paper (Refereed)
    Abstract [en]

    A total of 49 reinforced concrete beams of both high strength concrete (HSC) and, for reference, normal strength concrete (NSC) were tested. 38 beams were subjected to air blast loading in a shock tube and the remaining eleven beams were tested statically for reference. Concrete with nominal compressive cube strengths 40, 100, 140, 150 and 200 MPa were used and a few beams also contained steel fibres. Furthermore, beams with two concrete layers of different strength were tested. The purpose of this investigation was to study the structural behaviour of the concrete beams subjected to air blast loading.

    All beams subjected to static loading failed in flexure. In the dynamic tests, beams without fibres and with high ratios of reinforcement exhibited shear failure. It was observed that the inclusion of steel fibres in the matrix increased the shear strength and the ductility of the beams. This investigation indicates that beams subjected to air blast loading obtained an increased load capacity when compared to the corresponding beams subjected to static loading.

  • 12.
    Magnusson, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Hallgren, Mikael
    Tyréns AB.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Air-blast-loaded, high-strength concrete beams. Part I: Experimental investigation2010In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 62, no 2, p. 127-136Article in journal (Refereed)
    Abstract [en]

    The structural behaviour of concrete beams subjected to air blast loading was investigated. Beams of both high-strength concrete (HSC) and normal-strength concrete (NSC) were subjected to air blasts from explosives in a shock tube and for reference were also loaded statically. Concrete with nominal compressive strengths of 40, 100, 140, 150 and 200 MPa were used and a few beams also contained steel fibres. Furthermore, beams with two concrete layers of different strength were tested. All beams subjected to static loading failed in flexure. For some beam types, the failure mode in the dynamic tests differed from the failure mode in the corresponding static tests. In these cases, the failure mode changed from a ductile flexural failure in the static tests to a brittle shear failure in the dynamic tests. Beams without fibres and with high ratio of reinforcement exhibited shear failures in the dynamic tests. It was observed that the inclusion of steel fibres increased the shear strength and the ductility of the beams. The investigation indicates that beams subjected to air blast loading obtain an increased load capacity when compared with the corresponding beams subjected to static loading.

  • 13. Magnusson, Johan
    et al.
    Hallgren, Mikael
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Shear in concrete structures subjected to dynamic loads2014In: Structural Concrete, ISSN 1464-4177, E-ISSN 1751-7648, Vol. 15, no 1, p. 55-65Article in journal (Refereed)
    Abstract [en]

    Shear failures in reinforced concrete structures under intense dynamic loads are brittle and limit the structure's energy-absorbing capabilities. This paper comprises a review of the literature dealing with the problem of dynamic shear of reinforced concrete elements, with a focus on parameters that control flexural shear and direct shear. In this context, dynamic loads refer to intense events due to explosions and impacts. For this reason, the initial response is also highlighted. Experimental investigations and calculations show that shear force and bending moment distributions in dynamic events are initially significantly different from the distributions under slowly applied loads. Therefore, structural wave propagation, geometrical properties of elements, strain rate effects and dynamic load characteristics need to be considered when analysing shear. The review also indicates that arch action in the shear span soon after the load has been applied has a large influence on the shear capacity of an element. This action is of particular importance in intense loading events. Finally, suggestions for further research are identified.

  • 14.
    Magnusson, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Hallgren, Mikael
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. Tyréns.
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Numerical analyses of shear in concrete structures subjected to distributed blast loads2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Article in journal (Refereed)
  • 15.
    Magnusson, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Hansson, Håkan
    Totalförsvarets forksningsinstitut.
    Simulations of air blast loaded structural reinforced concrete elements2005Report (Other academic)
  • 16.
    Magnusson, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Hansson, Håkan
    Totalförsvarets forskningsinstitut.
    Simulering av explosionsbelastade betongbalkar - en principstudie2005Report (Other academic)
  • 17.
    Magnusson, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Hansson, Håkan
    Totalförsvarets forskningsinstitut.
    Skoglund, Peter
    Totalförsvarets forskningsinstitut.
    Unosson, Mattias
    Totalförsvarets forskningsinstitut.
    Material testing and numerical simulations of penetration in high performance concrete2002Report (Other academic)
  • 18.
    Magnusson, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Unosson, Mattias
    Totalförsvarets forskningsinstitut.
    Carlberg, Anders
    Totalförsvarets forskningsinstitut.
    High performance concrete "HPC"-field experiments and production2001Report (Other academic)
  • 19. Morales-Alonso, G.
    et al.
    Magnusson, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. Grontmij AB, Eskilstuna, Sweden .
    Hansson, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Gálvez, F.
    Sánchez-Gálvez, V.
    Behaviour of concrete structural members subjected to air blast loading2013In: Proceedings - 27th International Symposium on Ballistics, BALLISTICS 2013, 2013, Vol. 1, p. 936-947Conference paper (Refereed)
    Abstract [en]

    Numerical analysis is a suitable tool in the design of complex reinforced concrete structures under extreme impulsive loadings such as impacts or explosions at close range. Such events may be the result of terrorist attacks. Reinforced concrete is commonly used for buildings and infrastructures. For this reason, the ability to accurately run numerical simulations of concrete elements subjected to blast loading is needed. In this context, reliable constitutive models for concrete are of capital importance. In this research numerical simulations using two different constitutive models for concrete (Continuous Surface Cap Model and Brittle Damage Model) have been carried out using LS-DYNA. Two experimental benchmark tests have been taken as reference. The results of the numerical simulations with the aforementioned constitutive models show different abilities to accurately represent the structural response of the reinforced concrete elements studied.

  • 20.
    Nilsson, Martin
    et al.
    Totalförsvarets forskningsinstitut.
    Magnusson, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Splitterkarakterisering: hur gör man och vilken utrustning behövs?2009Report (Other academic)
1 - 20 of 20
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