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| 5. |
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| 6. |
- Amani, Mozhdeh, et al.
(författare)
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Shear Behavior of Stainless Steel Girders with Corrugated Webs
- 2022
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Ingår i: Proc. of Stainless Steel in Structures – Sixth International Experts Seminar.
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Konferensbidrag (refereegranskat)abstract
- This paper reports experimental and finite element investigations conducted to assess the shear strength of corrugated web girders in stainless steel. The steel under consideration is LDX 2101. Four trapezoidal corrugated web girders were tested under shear. All tested girders reached the shear yield strength followed by strain hardening. An imperfection sensitivity study was done with the aid of finite element modelling. It was observed that an initial geometric imperfection based on the first eigen buckling mode with a maximum amplitude of the minimum dimension of the critical corrugation sub panel divided by 200, ?max200⁄, leads to an ultimate shear strength greater than the shear yield strength and close to the test findings. It is concluded that EN 1993-1-5 shear design model for corrugated webs is conservative for stainless steel girders tested in the current study.
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| 7. |
- Amani, Mozhdeh, 1985, et al.
(författare)
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Shear behavior of stainless steel girders with corrugated webs
- 2023
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Ingår i: Journal of constructional steel research. - : Elsevier Ltd. - 0143-974X .- 1873-5983. ; 210
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the shear strength of corrugated web girders made of EN 1.4162/LDX 2101 stainless steel is investigated. Four full-scale trapezoidal corrugated web girders were tested under shear. Before conducting the tests, DIC was used to measure the real geometric imperfections in the web panels. Complementary finite element analysis studies were conducted to assess the sensitivity of the shear strength to initial imperfections. The experimental results indicated that all the tested girders with a local slenderness ratio of λ = 0.7 attained the shear yield strength, which was then followed by strain hardening in the material at a level that was 8–18% higher than the yield strength. This implies that the Eurocode's limit of λ = 0.25 to attain the plastic shear strength in corrugated webs can be quite conservative for stainless steel. According to the findings of the imperfection sensitivity studies, an initial geometric imperfection based on the first eigen buckling mode and with a maximum amplitude of amax/200, where amax is the maximum corrugation fold length, yielded ultimate strength within 3% of the test results. When the amplitude was increased to hw/200, where hw is the web height, the ultimate strength was estimated to be 25% lower on average than in the experiments. In three of the studied girders, initial imperfections with other forms than the first buckling mode were found to be more critical. Further, it was found that regardless of mode number, mode shapes that are more extended over the web panel result in a higher degradation of the ultimate shear strength. © 2023 The Authors
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| 8. |
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Analysis of the Flexural Behavior of Textile Reinforced Reactive Powder Concrete Sandwich Elements Using Optical Measurements
- 2018
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Proceedings (redaktörskap) (refereegranskat)abstract
- Prefabricated and non-load bearing sandwich façade elements were developed using Textile Reinforced Reactive Powder Concrete (TRRPC) along with low density Foamed Concrete (FC) and Glass Fiber Reinforced Polymer (GFRP) continuous connecting devices. Four-point bending tests were performed on large-scale TRRPC sandwich element beams to characterize the structural performance, which included the flexural capacity, level of composite action, resulting deformation, crack propagation and failure mechanisms. Optical measurements based on Digital Image Correlation (DIC) were taken simultaneously to enable a detailed analysis of the underlying composite action. The structural behavior of the developed elements was found to be highly dependent on the stiffness and strength of the connectors to ensure composite action between the two TRRPC panels.
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| 10. |
- Bergström, Gunnar, et al.
(författare)
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Acceptanskriterier för repor och intryck i plaströr Accpetance criteria for scratches and indentations in plastic pipes
- 2009
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Rapport (refereegranskat)abstract
- Development of materials and laying techniques have arisen the question how scratches and indentations in plastics pipes affect the strength and technical lifetime of pipelines. Scratches may occur both in the manufacturing of the pipes, in connection with the installation and subsequent maintenance. The problems in assessing the failure risk from scratches and indentations are similar for pipes used in gas and water distribution and in district heating applications. Therefore, a broad effort to identify the risks in relation to current pipe materials is technically and economically justified. The project has aimed to evaluate the effect of scratches and indentations on the technical lifetime of plastics pipes and to present criteria for maximum allowable depth of scratches and indentations. The study on pressure pipes focused on the conditions for scratched polyethylene pipes to achieve a lifetime of 50 years. It is noted that a scratch damage can not be judged solely on the basis of its depth and sharpness. To assess the impact of the scratch on the serviceability of the pipe, consideration must also be taken to the material from which the pipe was made and the safety factor used in the design. Extensive pressure tests show that pipes made of modern materials can withstand surface scratches to a higher degree than pipes of older materials. For pipes made of modern bimodal PE80 and PE100 materials, scratches up to 10% depth may be accepted without reduction of rated pressure. However, for pipes of older material, a reduction in pressure may be required already at smaller scratches. The study also indicates that for the same relative scratch depth, a greater reduction in pressure is required with increasing pipe dimension. The study on the non pressure pipes shows that the studied polypropylene pipes resist both deep scratches combined with ovalization and large indentations without any cracks penetrating the pipe wall. However, the extent and development of crazing and surface cracking vary with scratch depth, deformation level and material. The test pipes were subjected to extreme conditions very rarely or never occurring in practice. This suggests that small scratches at moderate ovalization and realistic indentations in temperatures around room temperature do not affect the lifetime of the pipes. One objective of the project was to develop a method for the evaluation of the scratch resistance of a pipe. In the proposed test method the force needed to produce a specified scratch is measured. This force is used as a relative measure of the scratch resistance of a pipe material when compared to other materials. In order to assess to what extent a scratch affects the lifetime of the pipe, the depth of the scratch must be estimated with reasonable accuracy. Since the scratch in many cases is found on existing pipelines the method must be suited for field use. To achieve that a simple instrument for scratch depth measurements was made and evaluated.
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| 11. |
- Bergström, Gunnar, et al.
(författare)
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Accpetance criteria for scratches and indentations in plastic pipes
- 2009
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Rapport (refereegranskat)abstract
- Development of materials and laying techniques have arisen the question how scratches and indentations in plastics pipes affect the strength and technical lifetime of pipelines. Scratches may occur both in the manufacturing of the pipes, in connection with the installation and subsequent maintenance. The problems in assessing the failure risk from scratches and indentations are similar for pipes used in gas and water distribution and in district heating applications. Therefore, a broad effort to identify the risks in relation to current pipe materials is technically and economically justified. The project has aimed to evaluate the effect of scratches and indentations on the technical lifetime of plastics pipes and to present criteria for maximum allowable depth of scratches and indentations. The study on pressure pipes focused on the conditions for scratched polyethylene pipes to achieve a lifetime of 50 years. It is noted that a scratch damage can not be judged solely on the basis of its depth and sharpness. To assess the impact of the scratch on the serviceability of the pipe, consideration must also be taken to the material from which the pipe was made and the safety factor used in the design. Extensive pressure tests show that pipes made of modern materials can withstand surface scratches to a higher degree than pipes of older materials. For pipes made of modern bimodal PE80 and PE100 materials, scratches up to 10% depth may be accepted without reduction of rated pressure. However, for pipes of older material, a reduction in pressure may be required already at smaller scratches. The study also indicates that for the same relative scratch depth, a greater reduction in pressure is required with increasing pipe dimension. The study on the non pressure pipes shows that the studied polypropylene pipes resist both deep scratches combined with ovalization and large indentations without any cracks penetrating the pipe wall. However, the extent and development of crazing and surface cracking vary with scratch depth, deformation level and material. The test pipes were subjected to extreme conditions very rarely or never occurring in practice. This suggests that small scratches at moderate ovalization and realistic indentations in temperatures around room temperature do not affect the lifetime of the pipes. One objective of the project was to develop a method for the evaluation of the scratch resistance of a pipe. In the proposed test method the force needed to produce a specified scratch is measured. This force is used as a relative measure of the scratch resistance of a pipe material when compared to other materials. In order to assess to what extent a scratch affects the lifetime of the pipe, the depth of the scratch must be estimated with reasonable accuracy. Since the scratch in many cases is found on existing pipelines the method must be suited for field use. To achieve that a simple instrument for scratch depth measurements was made and evaluated.
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| 12. |
- Chozas, Valle, et al.
(författare)
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Synthesis and characterization of reactive powder concrete for its application on thermal insulation panels
- 2015
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Ingår i: IOP Conference Series. - : Institute of Physics Publishing (IOPP).
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Konferensbidrag (refereegranskat)abstract
- This paper describes the synthesis and characterization of a set of textile reinforced reactive powder concrete (RPC) mixes that have been prepared in the framework of the SESBE project which aims to develop facade panels for the building envelope. In order to reduce the environmental impact, high concentration of type I and II mineral additions were added to the mixtures (up to 40% of cement replacement). The mechanical properties of the materials were analysed showing high values of compression strength thus indicating no disadvantages in the compression mechanical performance (∼140 MPa) and modulus of elasticity. In order to enable the use of these materials in building applications, textile reinforcement was introduced by incorporating layers of carbon fibre grids into the RPC matrix. The flexural performance of these samples was analysed showing high strength values and suitability for their further utilization.
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| 13. |
- Cinar, Ahmet, et al.
(författare)
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An autonomous surface discontinuity detection and quantification methodby digital image correlation and phase congruency
- 2017
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Ingår i: Optics and lasers in engineering. - : Elsevier BV. - 0143-8166 .- 1873-0302. ; 96, s. 94-106
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Tidskriftsartikel (refereegranskat)abstract
- Digital image correlation has been routinelyused to measure full-field displacements in many areas of solid mechanics,including fracture mechanics. Accurate segmentation of the crack path is neededto study its interaction with the microstructure and stress fields, and studiesof crack behaviour, such as the effect of closure or residual stress infatigue, require data on its opening displacement. Such information can beobtained from any digital image correlation analysis of cracked components, butit collection by manual methods is quite onerous, particularly for massiveamounts of data. We introduce the novel application of Phase Congruency to detectand quantify cracks and their opening. Unlike other crack detection techniques,Phase Congruency does not rely on adjustable threshold values that require userinteraction, and so allows large datasets to be treated autonomously. Theaccuracy of the Phase Congruency based algorithm in detecting cracks isevaluated and compared with conventional methods such as Heaviside function fitting.As Phase Congruency is a displacementbased method, it does not suffer from thenoise intensification to which gradient-based methods (e.g. strain thresholding)are susceptible. Its application is demonstrated to experimental data forcracks in quasi-brittle (Granitic rock) and ductile (Aluminium alloy)materials.
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| 14. |
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| 15. |
- Flansbjer, Mathias, et al.
(författare)
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3D Analysis of Strains in Fibre Reinforced Concrete Using X-Ray Tomography and Digital Volume Correlation
- 2017
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Konferensbidrag (refereegranskat)abstract
- In fibre reinforced concrete (FRC), understanding the underlying interaction mechanisms between discrete fibres and the surrounding concrete matrix can lead to the optimization of the fibre-matrix combination. This paper presents the initial development of a method enabling the analysis of this given interaction on ameso-mechanical level. The method is such that volume images are initially captured using X-ray Computed Tomography (XCT) on small-scale FRC specimens under loading which are thereafter analysed to measure full 3D strainand deformation via Digital Volume Correlation (DVC). It is anticipated that the method developed in this project can be a useful tool for the developmentof new innovative and high performance FRC.
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| 16. |
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| 17. |
- Flansbjer, Mathias, et al.
(författare)
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Analysis of Failure Modes in Fiber Reinforced Concrete Using X-rayTomography and Digital Volume Correlation
- 2018
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Konferensbidrag (refereegranskat)abstract
- Pull-out mechanisms for different common steel fibers were investigatedusing adapted pull-out tests performed in-situ in an x-ray micro tomograph(µXRT). High-resolution volume images from the µXRT scans enable clearvisualization of aggregates, pores, the fiber and the fiber-matrix interface.Furthermore, the natural density speckle pattern from aggregate distributionand pores was found suitable for Digital Volume Correlation (DVC) analysis.From the DVC results it was possible to visualize and quantify the straindistribution in the matrix around the fiber at the different load levels up tofinal failure, being marked by either pull-out or fiber rupture. This studydemonstrates that strain measurements within the concrete matrix can beobtained successfully using µXRT imaging and DVC analysis, which leads to anincreased understanding of the interaction mechanisms in fibre reinforcedconcrete under mechanical loading.
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| 18. |
- Flansbjer, Mathias, et al.
(författare)
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Analysis of Fiber-matrix Interaction in FRC using X-ray Tomography and Digital Volume Correlation
- 2019
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Ingår i: proc. of 10th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-X). - Bayonne, France : International Association of Fracture Mechanics for Concrete and Concrete Structures.
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Konferensbidrag (refereegranskat)abstract
- Fiber pull-out is generally considered to be the dominating failure mechanism in fiber reinforced concrete (FRC). Accordingly, pull-out tests are typically performed to characterize the fiber-matrix interaction. However, little direct insight can be gained on the actual mechanisms ofthe pull-out from such a test. Deeper understanding could however be gained through the addition of non-destructive techniques to pull-out tests to enable the visualization and quantification of the mechanical interaction. Pull-out mechanisms for different common steel fibers were investigated using adapted pull-out tests performed in-situ in an X-ray micro tomography (µXRT). High resolution volume images from the µXRT scans enable clear visualization of aggregates, pores, fiber and fiber-matrix interface. Furthermore, the natural density speckle pattern from aggregate distribution and pores was found to be suitable for Digital Volume Correlation (DVC) analysis. From the DVC results it was possible to visualize and quantify the strain distribution in the matrix around the fiber at different load levels up to final failure, being marked by either pull-out or fiber rupture. The load transfer mechanism was initially dominated by shear along the fiber. As the load increased, slip occurred in the end-hook region and mechanical locking became the governing mechanism. This study demonstrates that strain measurements within the concrete matrix and passive end-slip can be obtained successfully using µXRT imaging and DVC analysis, which leads to an increased understanding of the interaction mechanisms in fiber reinforced concrete under mechanical loading.
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| 20. |
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| 21. |
- Flansbjer, Mathias, et al.
(författare)
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Composite Behaviour of Textile Reinforced Reactive Powder Concrete Sandwich Façade Elements
- 2018
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Ingår i: International Journal of Concrete Structures and Materials. - : Springer Science and Business Media LLC. - 1976-0485 .- 2234-1315. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Within the EC funded project smart elements for sustainable building envelopes, carbon textile reinforcement was incorporated into reactive powder concrete, namely textile reinforced reactive powder concrete (TRRPC), to additionally improve the post-cracking behaviour of the cementitious matrix. This high-performance composite material was included as outer and inner façade panels in prefabricated and non-load bearing sandwich elements along with low density foamed concrete (FC) and glass fibre reinforced polymer continuous connecting devices. Experiments and finite element analysis (FEA) were applied to characterize the structural performance of the developed sandwich elements. The mechanical behaviour of the individual materials, components and large-scale elements were quantified. Four-point bending tests were performed on large-scale TRRPC-FC sandwich element beams to quantify the flexural capacity, level of composite action, resulting deformation, crack propagation and failure mechanisms. Optical measurements based on digital image correlation were taken simultaneously to enable a detailed analysis of the underlying composite action. The structural behaviour of the developed elements was found to be highly dependent on the stiffness and strength of the connectors to ensure composite action between the two TRRPC panels. As for the FEA, the applied modelling approach was found to accurately describe the stiffness of the sandwich elements at lower load levels, while describing the stiffness in a conservative manner after the occurrence of connector failure mechanisms. © 2018, The Author(s).
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| 22. |
- Flansbjer, Mathias, et al.
(författare)
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Mechanical behaviour of concrete piles affected by sulphate attack
- 2013
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Ingår i: Proceeding of the International IABSE Conference. - 9783857481239 ; , s. 389-392, s. 556-557
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Konferensbidrag (refereegranskat)abstract
- Assessing the remaining service life is vital for the planning of maintenance of concrete constructions in aggressive environments. Here we present results from testing of two concrete piles affected by sulphate attack in marine environment. A multi-method approach going from micro scale to structural level has been applied. The crack propagation was monitored during loading by means of DIC and AE. After the test crack patterns was studied using fluorescence microscopy. Furthermore, non-linear finite element analysis at the structural level was used to study the influence of the chemical attack on the response of concrete piles.
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| 23. |
- Flansbjer, Mathias, et al.
(författare)
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Mechanical behaviour of concrete piles affected by sulphate attack
- 2012
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Ingår i: Proceeding of fib Symposium: Concrete Structures for Sustainable Community, 11 – 12 June 2012, Stockholm, Sweden. ; , s. 389-392
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Konferensbidrag (refereegranskat)abstract
- Assessing the remaining service life is vital for the planning of maintenance of concrete constructions in aggressive environments. Here we present results from testing of two concrete piles affected by combined sulphate and chloride attack in marine environment. A multi method approach going from micro scale to structural level has been applied. The crack propagation was monitored during loading by means of DIC and AE. After the test crack patterns was studied using fluorescence microscopy. Furthermore, non-linear finite element analysis at the structural level was used to study the influence of the chemical attack on the response of concrete piles.
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| 24. |
- Flansbjer, Mathias, et al.
(författare)
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Meso Mechanical Study of Cracking Process in Concrete Subjected toTensile Loading
- 2018
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Ingår i: Nordic Concrete Research. - Oslo : Walter de Gruyter GmbH. - 0800-6377 .- 2545-2819. ; 59:2, s. 13-29
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This project focused on how the cracking process in concrete is influenced by both the micro and meso structures of concrete. The aim was to increase knowledge pertaining to the effect of critical parameters on the cracking process and how this is related to the material's macroscopic properties. A methodology based on the combination of different experimental methods and measuring techniques at different scales was developed. Crack propagation during tensile loading of small-scale specimens in a tensile stage was monitored by means of Digital Image Correlation (DIC) and Acoustic Emission (AE). After testing, crack patterns were studied using fluorescence microscopy.
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| 25. |
- Flansbjer, Mathias, et al.
(författare)
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Methodology for Mesomechanical Study of Concrete Material
- 2017
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Konferensbidrag (refereegranskat)abstract
- This project focuses on detailed studies of how the cracking process in concrete is influenced by the concrete micro- and mesostructure. The aim is to increase knowledge of how critical parameters affect the cracking process and how this is related to the material's macroscopic properties. A methodology based on the combination of different experimental methods and measuring techniques at different scale levels has been developed. Crack propagation during tensile loading of small-scale specimens in a tensile stage was monitored by means of Digital Image Correlation (DIC) and Acoustic Emission (AE). After the test, crack patterns were studied using fluorescence microscopy.
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| 26. |
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| 27. |
- Flansbjer, Mathias, et al.
(författare)
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Quantitative Characteristics in Shear Load
- 2011
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Ingår i: <em>fib</em> Symposium PRAGUE 2011 - Proceedings. ; , s. 567-570
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 28. |
- Flansbjer, Mathias, et al.
(författare)
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Quantitative fracture characteristics in shear load
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Today, no general design method for shear strength capacity of RC beams can predict the failure load with a high degree of accuracy. The failure load between two beams cast from the same batch may vary as much as 30 percent. This project aims at investigating factors affecting the shear strength capacity based on an understanding of micro and meso scale material properties. Tests were performed on beams with two different types of aggregate and two different w/c. The crack propagation was monitored during the loading by means of DIC and AE. The results show that the use of natural aggregates or crushed aggregates as finer fractions strongly affect the shear strength capacity. From direct shear tests it was found that the scatter of the shear strength was much higher for the specimens with natural aggregates compared with crushed aggregates. The same tendency was found for the shear crack initiation load for the RC beams. The percentage of fractures propagating through aggregate, paste and the ITZ varied with w/c, type of aggregate and type of failure. Microscopy in combination with DIC and AE measurements makes it possible to determine at what stage different cracks have been formed and their relation to the micro structure.
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| 29. |
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| 30. |
- Flansbjer, Mathias
(författare)
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Rörställningar - Utvärdering av typfall
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Tube and coupler scaffolds - Evaluation of typeconfigurationsTube and coupler scaffolds are frequently used as facade scaffolds. The design and stability of the scaffold is of great importance for the safety of the workers using the scaffold. According to Swedish regulation, facade scaffolds made of prefabricated elements have to be subjected to type examination. This requirement does not include tube and coupler scaffolds. Instead, these are to be designed in accordance with type-configurations given in the Swedish code or by using the same principles as in these configurations. However, these type-configurations are old-fashioned and do not fulfil modern requirements regarding design and safety of work. The aim of this project was to prepare new type-configurations for tube and coupler scaffolds using European standards for design of facade scaffolds. Finite element analyses have been used to evaluate the load carrying capacity of different scaffold configurations. The result of this project may be used as a basis for revision of the type-configurations for tube and coupler scaffolds in the Swedish code.
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| 31. |
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| 32. |
- Flansbjer, Mathias, et al.
(författare)
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Structural Concept of Novel RPC Sandwich Façade Elements with GFRP Connectors
- 2016
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Ingår i: IABSE Congress Stockholm 2016. - : IABSE c/o ETH Hönggerberg. - 9783857481444 ; , s. 2164-2171
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Konferensbidrag (refereegranskat)abstract
- The SESBE research project aims to develop novel smart sandwich façade elements with high insulating capabilities while providing a reduced thickness in conjunction with superior mechanical and durability properties. The present paper mainly focuses on the verification of the mechanical performance of the glass fibre reinforced polymer (GFRP) connectors in the façade element composed of reactive powder concrete (RPC) panels with foam concrete insulation between them. Because of the reduced thickness of the large façade elements, the performance of the connectors is critical for the entire structural concept. A description of structural performance and results based on experimental methods and finite element (FE) analysis are presented.
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| 33. |
- Flansbjer, Mathias, et al.
(författare)
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Strutural performance of GFRP connectors in Composite sandwich facade elements
- 2016
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Ingår i: Journal of Facade Design and Engineering. - 2213-302X .- 2213-3038. ; 4:1-2, s. 35-52
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Tidskriftsartikel (refereegranskat)abstract
- A systematic testing and modelling program has been developed for the verification of the structural performance of facade sandwich elements to take structural aspects into consideration in the SESBE research project, focusing on the development of “smart” facade elements.The present paper mainly focuses on the verification of the mechanical performance of the glass fibre reinforced polymer (GFRP) connectors of the novel type of facade element composed of reactive powder concrete (RPC) panels with foam concrete insulation between them. Because of the reduced thickness of the large facade elements, the performance of the connectors is critical for the entire structural concept. The first series of the testing and modelling programme concerning connector performance are presented here. The results suggest that sufficient strength and ductility of the connectors can be ensured using GFRP in the proposed thin light-weight facade elements.
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| 34. |
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| 35. |
- Flansbjer, Mathias, et al.
(författare)
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Tests on BCE
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 36. |
- Flansbjer, Mathias, et al.
(författare)
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Textile reinforced concrete sandwich panels
- 2012
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Ingår i: fib Symposium 2012: Concrete Structures for Sustainable Community - Proceedings. - Stockholm : Swedish Conrete Association. - 9789198009811 ; , s. 169-172
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Konferensbidrag (refereegranskat)abstract
- The main reason for the thickness of a concrete sandwich element is the requirement for the protective concrete cover for the steel reinforcement. By changing the steel reinforcement to non-corrosive textile fibre net this requirement could be strongly reduced. Use of textile reinforced concrete (TRC) makes it possible to produce much thinner and slimmer concrete facades in the future without changing their mechanical properties. This article presents selected results from Tekocrete project (Formas-BIC) concerning pilot production, modelling and full-scale testing of new light weight sandwich elements reinforced with AR glass and carbon fibre nets.
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| 37. |
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| 38. |
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| 39. |
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| 40. |
- Flansbjer, Mathias, et al.
(författare)
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Verification of the structural performance of textile reinforced reactive powder concrete sandwich facade elements
- 2019
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 9:12
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Tidskriftsartikel (refereegranskat)abstract
- As a part of the SESBE (Smart Elements for Sustainable Building Envelopes) project, non-load bearing sandwich elements were developed with Textile Reinforced Reactive Powder Concrete (TRRPC) for outer and inner facings, Foam Concrete (FC) for the insulating core and Glass Fiber Reinforced Polymer (GFRP) continuous connectors. The structural performance of the developed elements was verified at various levels by means of a thorough experimental program coupled with numerical analysis. Experiments were conducted on individual materials (i.e., tensile and compressive tests), composites (i.e., uniaxial tensile, flexural and pull-out tests), as well as components (i.e., local anchorage failure, shear, flexural and wind loading tests). The experimentally yielded material properties were used as input for the developed models to verify the findings of various component tests and to allow for further material development. In this paper, the component tests related to local anchorage failure and wind loading are presented and coupled to a structural model of the sandwich element. The validated structural model provided a greater understanding of the physical mechanisms governing the element's structural behavior and its structural performance under various dead and wind load cases. Lastly, the performance of the sandwich elements, in terms of composite action, was shown to be greatly correlated to the properties of the GFRP connectors, such as stiffness and strength
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| 41. |
- Flansbjer, Mathias, et al.
(författare)
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Visual assessment of fire damaged concrete
- 2011
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Ingår i: BrandPosten. ; :44, s. 12-13
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Fire can reduce the load-carrying capacity of concrete structures. A new innovative method, Optical Deformation Measurement, can be used to determine how far into the concrete damage has penetrated. The method involves measurements on test cores from the damaged structure.
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| 42. |
- Godio, Michele, et al.
(författare)
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Experimental and numerical approaches to investigate the out-of-plane response of unreinforced masonry walls subjected to free far-field blasts
- 2021
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Ingår i: Engineering structures. - : Elsevier. - 0141-0296 .- 1873-7323. ; 239
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Forskningsöversikt (refereegranskat)abstract
- Masonry walls are bulky and heavy and have therefore the potential to act naturally as a protective system to blasts. Yet, they are known to have a limited flexural and torsional capacity, particularly when unreinforced. When exposed to shockwaves, they experience out-of-plane failure mechanisms which may affect the overall stability of the building and engender flying debris inside the building. The out-of-plane response of unreinforced masonry walls to blasts depends on many factors characterizing both the wall and blast action, making any sort of prediction difficult. In this context, experimental tests and numerical models become key tools that can be used to study the wall’s response on a case-by-case basis. This review covers the major experimental and numerical approaches to assess the out-of-plane response of unreinforced masonry walls subjected to blasts. A methodological appraisal is used for the test methods, focusing on the preparation of the test items and test setup, the boundary conditions and failure mechanisms investigated, as well as the commonly employed measurement techniques. The survey on the modelling approaches includes key topics such as level of detail and cost, and reports strategies to model the wall and blast scenario. The review provides a thematic analysis of the available literature, aimed to assist the analyst in selecting a suitable tool for the investigation of masonry in the field of blast engineering. Furthermore, the findings presented herein can support amendments of existing codes and guidelines pertaining to the design of protective masonry structures.
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| 43. |
- Godio, Michele, et al.
(författare)
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Low-velocity out-of-plane impact tests on double-wythe unreinforced brick masonry walls instrumented with optical measurements
- 2023
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Ingår i: International Journal of Impact Engineering. - 0734-743X .- 1879-3509. ; 178
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Tidskriftsartikel (refereegranskat)abstract
- Unreinforced brick masonry makes up today a significant piece of the European built environment, including not only residential buildings but also strategically important structures that are not designed to withstand blasts and impacts. Yet, it is difficult to accurately estimate the response of these structures and the extent of damage they sustain during such extreme loading conditions. This paper presents the implementation and discusses the results of laboratory impact tests conducted on natural-scale double-wythe unreinforced brick masonry walls, a typology that is frequently found in Northern Europe. The walls were spanning vertically between two reinforced concrete slabs and were subjected to low-velocity drop-weight pendulum tests in which they were repeatedly hit until the opening of a breach in the center of the wall. The tests were instrumented with both hard-wired and optical measurements, the latter consisting of high-speed cameras and digital image correlation techniques, to face the difficulty of observing cracks and determining the deflections of the walls with adequate accuracy at the time of the impact. Investigated in these tests were the out-of-plane response of the walls and their capacity to resist the impacts. The axial load applied on the top of the walls was varied for two wall configurations and monitored throughout the tests to study the effect of arching on the failure mechanism produced and number of repeated hits needed to open the breach. Of interest was also the evidence of cracking, more specifically the way it initiated on the undamaged walls and next propagated upon consecutive hits. The data generated from these tests are made available to support further investigations on unreinforced masonry structures subjected to extreme actions.
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- Godio, Michele, et al.
(författare)
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Single- and double-wythe brick masonry walls subjected to four-point bending tests under different support conditions : Simply supported, rigid, non-rigid
- 2023
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Ingår i: Construction and Building Materials. - 0950-0618 .- 1879-0526. ; 404
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Tidskriftsartikel (refereegranskat)abstract
- Out-of-plane actions cause confined unreinforced masonry walls (URM) to develop what is known as an arching action. The role of arching is central in the resisting mechanisms of a wall; it contributes significantly to its loadbearing capacity as long as the wall’s deflections are minor, but gradually loses effect with increasing deflections, until collapse occurs. To date, limited experimental data is available on how arching develops in relation to the out-of-plane behaviour of the wall. This study brings new experimental evidence to this aspect. Quasi-static monotonic four-point bending tests were conducted on eleven brick wall strips, with reinforced concrete (RC) slabs affixed below and over the walls to simulate contact conditions of a typical construction system. The walls were tested vis-à-vis three different support conditions: simply supported, rigid, and non-rigid. The influence of these support conditions on the out-of-plane behaviour of the walls was studied on specimens with varying thickness – single and double wythe – and subjected to different levels of axial compression (or overload). While the former support condition was designed not to yield any arching inside the wall (unconfined masonry), the intermediate and latter solutions generated an arching action that was proportional respectively to the elongation of the wall (partially confined masonry), and its deflection (confined masonry). The walls were tested inside a bi-axial test setup that allowed not only the out-of-plane force but also the arching action to be measured, corroborating its central role in the development of the out-of-plane capacity of the walls. To support the observations, deformation characteristics and crack distributions were determined using two optical measurement systems placed in front and to the side of the walls, making use of the Digital Image Correlation (DIC) technique. The results of the tests are discussed in terms of failure mechanism as well as force and displacement capacity of the walls in relation to the investigated parameters. The test data is collected and made available to help with future research on the out-of-plane capacity of URM walls.
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