| 1. |
- Claeson-Jonsson, Christina, 1967, et al.
(author)
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Slender concrete columns subjected to sustained and short-term eccentric loading
- 2000
-
In: ACI Structural Journal. - 0889-3241. ; 97:1, s. 45-52
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Journal article (peer-reviewed)abstract
- A test series examining the structural behavior of six slender reinforced concrete columns subjected to short-term and sustained loading is presented. The columns had cross sections 200 x 200 mm and were 4 m long. Concrete strengths used were 35 and 92 MPa with a load eccentricity of 20 mm. Key parameters such as concrete strength, concrete and steel strains, cracking, midheight deflection, and loading rate were studied. The high-strength (HSC) columns subjected to short-term loading displayed less ductility and more sudden failures than the normal strength concrete (NSC) columns. Furthermore, the tests conducted indicated that the structural behaviour of the HSC is favorable under sustained loading, i.e., the HSC column exhibited less tendency to creep and could sustain the axial load without much increase in deformation for a longer period of time. An analysis based on a simplified stability analysis, using a stress-strain relation for concrete that includes creep, aging, and the confining effect of the stirrups was carried out. The model was shown to simulate the load-deflection curves satisfactorily for all of the concrete columns.
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| 2. |
- Fall, David, 1983, et al.
(author)
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Non-linear Finite Element Analysis of Steel Fibre Reinforced Beams with Conventional Reinforcement
- 2012
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In: 8th RILEM International Symposium on Fiber Reinforced Concrete: challenges and opportunities (BEFIB 2012). - 9782351581322 ; , s. 1033-1045
-
Conference paper (peer-reviewed)abstract
- The purpose of this study has been to investigate the behavior of elements reinforced with both conventional steel reinforcement and steel fibres in order to support future applications of such composites. Three beams of varying fibre content were tested in four-point bending. The results were then compared with results from nonlinear FE-analyses and the calculation method suggested in fib Model Code 2010. The beams were a part of a larger experimental programme where relevant properties were investigated in uniaxial tension tests and pull-out tests. The FE-modeling was performed using a two dimensional plane stress model. General agreement between experiments and the FE-analyses was obtained with regard to load-displacement behavior. The crack patterns from the FE-analysis and experiments agreed in general, although the crack patterns in the analysis were more distributed close to the reinforcement. Crack localization was enhanced by modifying the bond-slip behavior to include the bond loss at yielding. Calculations in accordance with fib Model Code 2010 yield conservative results in comparison with both experiments and FE-analysis.
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| 3. |
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| 4. |
- Fall, David, 1983, et al.
(author)
-
Reinforcing tailor-made concrete structures: Alternatives and challenges
- 2012
-
In: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 44, s. 372-378
-
Journal article (peer-reviewed)abstract
- Recent advances in automated concrete production make it possible to produce geometrically complex concrete structures. The purpose of this paper is to review reinforcement alternatives suitable for such structures and to analyse the problems associated with the geometrical complexity, not only in the reinforcement itself, but also in design. A review of the literature on reinforcement alternatives and governing standards shows that conventional steel reinforcement load bearing structures cannot easily be set aside. Any deviation from the standard structural elements, e.g. beams, walls and slabs, introduces design problems for most structural engineers. Approaches to problems of this complex nature are discussed here. Further developments needed are indicated: being able to choose the reinforcement direction, and optimisation with regard to parameters other than the reinforcement amount, e.g. feasibility of production. Furthermore, the need for a rational design process is discussed and some key issues, such as software incompatibilities are raised.
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| 5. |
- Fall, David, 1983, et al.
(author)
-
Skräddarsydda betongkonstruktioner
- 2010
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In: Bygg & Teknik. - 0281-658X. ; 2010:7:2010:7 Oktober, s. 20-22
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Journal article (other academic/artistic)abstract
- Att kunna skräddarsy betongkonstruktioner, så att man på ett rationellt sätt kan ta tillvara betongens formbarhet i olika konstruktioner är målet med EU-projektet TailorCrete. Med moderna hjälpmedel är det är idag fullt möjligt att, med hjälp av en industrirobot, direkt från en tredimensionell modell fräsa ut betongformer i formsand eller cellplast. Detta har i forskningssyfte utförts i forskningsprojektet Unikabeton (www.unikabeton.dk) av bland annat. Teknologisk Institut och Mærsk Mc-Kinney Møller Instituttet på Syddansk Universitet. Genom att tillämpa sådan modern teknik undviks avancerade handgjorda formverk, vilka idag är tidsödande, dyra och stället höga krav på hantverksskicklighet.
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| 6. |
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| 7. |
- Fang, Congqi, 1963, et al.
(author)
-
Bond behaviour of corroded reinforcing steel bars in concrete
- 2006
-
In: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 36:10, s. 1931-1938
-
Journal article (peer-reviewed)abstract
- The effect of steel corrosion on bond between steel bars and the surrounding concrete was investigated for different corrosion levels. Both pullout tests and finite element analysis were used and the results from the two were compared. An electrolyte corrosion technique was used to accelerate steel corrosion. For confined deformed bars, a medium level (around 4%) of corrosion had no substantial influence on the bond strength, but substantial reduction in bond took place when corrosion increased thereafter to a higher level of around 6%. It is demonstrated that the confinement supplied an effective way to counteract bond loss for corroded steel bars of a medium (around 4% to 6%) corrosion level. The results of finite element analyses, where it was assumed that rust behaved like a granular material, showed a reasonably good agreement with the experiments regarding bond strength and bond stiffness.
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| 8. |
- Fang, Congqi, 1963, et al.
(author)
-
Effect of corrosion on bond in reinforced concrete under cyclic loading
- 2006
-
In: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 36:3, s. 548-555
-
Journal article (peer-reviewed)abstract
- Cyclic loading can result in severe deterioration in the bond between reinforcing steel bar and the surrounding concrete, especially when the reinforcement is corroded. In this study, tests were carried out for bond stress-slip response of corroded reinforcement with concrete under cyclic loading. Parameters investigated include: corrosion level, confinement, bar type, and loading history. The results revealed that bond behaviour was significantly reduced under cyclic loading. Degradation in bond was significantly less for deformed bars than for smooth bars at the initial loading cycle, but the difference was diminished with loading. The bond reduction was more substantial for unconfined steel bars than for confined bars. The relatively high level of corrosion caused degradation primarily in the initial five cycles, the effect of corrosion being decreased with loading. It was also demonstrated that the cyclic bond stress-slip curves depended on loading history.
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| 9. |
- Fang, Congqi, 1963, et al.
(author)
-
The effect of corrosion on concrete bridges
- 2004
-
In: Bridge Maintenance, Safety, Management and Cost / edited by Eiichi Watanabe, Dan M. Frangopol, Tomoaki Utsunomiya. - 9058096807
-
Conference paper (peer-reviewed)
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| 10. |
- Grassl, Peter, 1974, et al.
(author)
-
A damage-plasticity model for the dynamic failure of concrete
- 2011
-
In: 8th International Conference on Structural Dynamics, Leuven, Belgium.
-
Conference paper (peer-reviewed)abstract
- A constitutive model based on the combination of damage mechanics and plasticity is developed to analyse concretestructures subjected to dynamic loading. The aim is to obtain a model, which requires input parameters with clear physicalmeanings. The model should describe the important characteristics of concrete subjected to multiaxial and rate-depending loading.This is achieved by combining an effective stress based plasticity model with an isotropic damage model based on plastic andelastic strain measures. The model response in tension, uni-, bi- and tri-axial compression is compared to experimental results inthe literature.
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| 11. |
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| 12. |
- Grassl, Peter, 1974, et al.
(author)
-
CDPM2: A damage-plasticity approach to modelling the failure of concrete
- 2013
-
In: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683. ; 50:24, s. 3805-3816
-
Journal article (peer-reviewed)abstract
- A constitutive model based on the combination of damage mechanics and plasticity is developed to analyse the failure of concrete structures. The aim is to obtain a model, which describes the important characteristics of the failure process of concrete subjected to multiaxial loading. This is achieved by combining an effective stress based plasticity model with a damage model based on plastic and elastic strain measures. The model response in tension, uni-, bi- and triaxial compression is compared to experimental results. The model describes well the increase in strength and displacement capacity for increasing confinement levels. Furthermore, the model is applied to the structural analyses of tensile and compressive failure.
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| 13. |
- Grassl, Peter, 1974, et al.
(author)
-
Concrete in compression: A plasticity theory with a novel hardening law
- 2002
-
In: International Journal of Solids and Structures. - 0020-7683. ; 39:20, s. 5205-5223
-
Journal article (peer-reviewed)abstract
- This paper deals with the modelling of the behaviour of plain concrete in triaxial compression using the theory of plasticity. The aim is to model the load resistance and the deformation capacity in uniaxial, biaxial and triaxial compression by means of few parameters, which can be determined easily.A novel hardening law based on a non-associated flow rule and the volumetric plastic strain as hardening parameter is combined with a yield surface proposed by Menetrey and William (1995). The novel hardening and softening law differs from a classic strain-hardening law, as instead of the length of the plastic strain vector only the volumetric component of the latter is used as a hardening parameter. Thus, the non-linearity of the plastic potential is utilized to describe the influence of multiaxial compression on the deformation capacity and no additional ductility measure is required.The implementation and calibration of the novel hardening law are discussed. The prediction of the model is compared to results of uniaxial, biaxial and triaxial compression tests. It is shown that with one set of calibration parameters a good prediction of the load resistance and the deformation capacity for all three types of compression tests can be achieved.
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| 14. |
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| 15. |
- Gylltoft, Kent, 1945, et al.
(author)
-
Tests to determine the modulus of elasticity for CFRP confined concrete columns in stage above the bearing capacity of unconfined concrete
- 2006
-
Reports (other academic/artistic)abstract
- This study covered investigations into the compressive behaviors of concretes strengthened by CFRP of various qualities. Concrete of three strengths were used - 20, 40 and 60MPa in cubic strength. The confined specimens had the size of diameter: 150, 250, 350mm keeping the shape ratio of height to diameter = 3 unchanged. The wrapping was 3, 5 and 7 layers for small size specimens (150mm x 450mm) and 5 layers for medium size (250mm x 750mm). The results were that no scale effect was observed between two dimension ratios of concrete samples. It was shown that the loading paths in the normalized stress space merge to the single master curve determined by the line of the concrete strength as function of the lateral pressure. From this observation follows, that in the nonlinear region the tangent modulus of the confined concrete E2 and differential Poisson ratio a can be expressed a simple formulae. The non-dimensional parameter is a function of only non-dimensional parameter , where the lateral modulus El = Ej h/R ( - radius of specimen, - thickness of carbon confinement, - modulus of confinement). The confined column breaks when the stress in the composite jacket reaches its critical level.
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| 16. |
- Jansson, Anette M, 1963, et al.
(author)
-
Applying a fracture mechanics approach on FRC beams, material testing and structural analysis
- 2008
-
In: Submitted to Journal of Advanced Concrete Technology.
-
Journal article (other academic/artistic)abstract
- The presented work has been focused on strain-softening FRC and the interrelationship between material properties and structural behaviour. The main purpose of this work was to establish a procedure for structural analysis of flexural members with a combination of steel fibres and conventional reinforcement. A systematic approach for material testing and structural analysis, based on fracture mechanics, has been used and this covers: (1) material testing; (2) inverse analysis; (3) adjustment of the -w relationship for fibre efficiency; and (4) cross-sectional and structural analysis. The results suggest that the approach used for the material testing provides the necessary properties to perform analyses based on non-linear fracture mechanics. The structural behaviour could be predicted with good agreement with FEM using both bi-linear and multi-linear -w relationships. When comparing the peak loads obtained in the experiments with the results from the analyses, the agreement was good, with a high correlation. This demonstrates the strength of the fracture-mechanics approach for material testing and structural analysis.
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| 17. |
- Jansson, Anette M, 1963, et al.
(author)
-
Applying a fracture mechanics approach to material testing and structural analysis of FRC beams
- 2007
-
In: Conference proceedings for FRAMCOS-6, Catania, Italy June 2007. ; , s. 1491-1496
-
Conference paper (peer-reviewed)abstract
- The presented work has been focused on strain-softening FRC and the interrelationship between material properties and structural behaviour. The main purpose of this work was to establish a procedure for structural analysis of flexural members with a combination of conventional reinforcement and steel fibres. A systematic approach for material testing and structural analysis, based on fracture mechanics has been used, this covers: (1) material testing; (2) inverse analysis; (3) adjustment of the -w relationship for fibre efficiency; and (4) cross-sectional and structural analysis. The results suggest that the approach used for the material testing provides the necessary properties to perform analyses based on non-linear fracture mechanics. The structural behaviour could be predicted with good agreement, using both FEM and an analytical model, and when comparing the peak loads obtained in the experiments with the results from the analyses, the agreement was good, with a high correlation. Hence, this demonstrates the strength of the fracture-mechanical approach for material testing and structural analysis.
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| 18. |
- Jansson, Anette M, 1963, et al.
(author)
-
Bond between Reinforcement and Self-Compacting Steel-Fibre-Reinforced Concrete
- 2012
-
In: Proceeding of the Fourth International Conference on Bond in Concrete 2012: Bond, Anchorage, Detailing. ; 1, s. 323-329
-
Conference paper (peer-reviewed)abstract
- In this study, pull-out tests of specimens with short embedment length and varying fibre content were carried out. The results showed no effect from the fibres on the bond-slip behaviour before peak load when normalized with respect to the compressive strength. After peak, the fibre reinforcement provided extra confinement, changing the failure mode from splitting to pull-out failure. The test results were used to calibrate a frictional bond model in non-linear finite element analyses. The model proved to yield results in good agreement with the experimental results regarding failure modes, load-slip relation and splitting strains on the surfaces of the pull-out specimens. The tests and analyses in combination confirmed that the fibre reinforcement neither disturbed nor improved the bond properties at the interface layer between reinforcement steel and concrete; i.e. the fibres only provided confinement to the surrounding structure.
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| 19. |
- Jansson, Anette M, 1963, et al.
(author)
-
Bond of reinforcement in self-compacting steel-fibre-reinforced concrete
- 2012
-
In: Magazine of Concrete Research. - : Thomas Telford Ltd.. - 1751-763X .- 0024-9831. ; 64:7, s. 617-630
-
Journal article (peer-reviewed)abstract
- Crack control, one of the main benefits of using fibre reinforcement, depends to a large extent on the concrete-rebar bond. Pull-out tests of specimens with short embedment length were carried out and the results showed no effect from the fibres on the normalised bond-slip behaviour before peak load. After this, the fibre reinforcement provided extra confinement, changing the failure mode from splitting to pull-out failure. The test results were used to calibrate a finite-element bond model that considers both tangential stresses and stresses in the radial direction from the rebar. Splitting cracks may be thus considered in the finite-element analyses. The model proved to yield results in good agreement with the experimental results regarding failure mode, load-slip relation and splitting strains on the surfaces of the pull-out specimens. The analyses revealed that two types of action were active in the cracking process. In addition, the confinement effect of the fibre reinforcement was compared with the confinement of conventional stirrups using the bond model in CEB-FIP model code 2010.
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| 20. |
- Jansson, Anette M, 1963, et al.
(author)
-
Design methods of fibre reinforced concrete: a state-of-the-art review
- 2008
-
In: Submitted to Nordic Concrete Research.
-
Journal article (other academic/artistic)abstract
- The increasing interest in the use of fibre reinforcement has created a need for established design and analysis methods. Fibre reinforcement is mainly used in applications such as industrial floors and sprayed concrete, although other application areas exist. Apart from increased load carrying capacity, one of the main benefits of adding fibres to concrete is the potential reduction in crack width, which depends on the amount of fibres added and positively affects the durability of the finished structure. By comparing ten design methods proposed by technical committees, this paper provides a basis for further research aimed at developing a common design basis. Evaluation is based on the way the fibre capacity is considered. In addition, a “good” design method should also consider all (or most) design situations. It was found that, for design, the Italian proposal provides comprehensiveness. However, some amendments are needed, e.g. a suggestion is that the proposed formula for calculating crack width/crack spacing be modified to also consider the residual tensile strength.
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| 21. |
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| 22. |
- Jansson, Anette M, 1963, et al.
(author)
-
Experimental investigation of surface crack initiation, propagation and tension stiffening in self-compacting steel–fibre-reinforced concrete
- 2012
-
In: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 45:8, s. 1127-1143
-
Journal article (peer-reviewed)abstract
- To investigate crack initiation and propagation in reinforced, self-compacting, steel–fibre-reinforced concrete (SCSFRC) members, tie elements were tested in tension. Strain and surface crack formation were monitored with an optical strain measurement system based on digital image correlation. In addition, to capture the softening behaviour (s–w) of the material, uni-axial tension testing was performed on SCSFRC cylinders. The results show that, with the optical strain measurement system, it was possible to detect different cracking modes and to follow the crack growth. It was especially of interest to recognize that high fibre amounts tend to change a sudden opening of a crack (as in non-fibrous concrete) into a more stable procedure. It was found that, for a given crack width, the SCSFRC specimens exhibited a noticeably higher tension stiffening than the specimens without fibres. Moreover, at a given load, the crack widths decreased by as much as 65% for the SCSFRC specimens with a nominal fibre content of 1%. For the uni-axial tension tests the results showed that with higher fibre content, for this type of fibre and concrete, both the peak stress and the residual tensile stress were increased. Additionally, it was noted for both specimen types that the scatter in fibre distribution decreased with increasing fibre content.
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| 23. |
- Jansson, Anette M, 1963, et al.
(author)
-
Flexural Behaviour of members with a combination of steel fibres and conventional reinforcement
- 2010
-
In: Nordic Concrete Research. - 0800-6377. ; 2/2010:42, s. 155-171
-
Journal article (peer-reviewed)abstract
- The purpose of the presented work was to investigate the flexural behaviour of members with a combination of steel fibres and conventional reinforcement. A systematic approach for material testing and structural analysis, based on fracture mechanics, was used and covers (1) material testing, (2) inverse analysis and (3) structural analysis based on FEM. In addition, the average crack spacing from the FE analyses was compared with experimental results and with two analytical approaches. The results suggest that the approach used for the material testing provides the properties necessary to perform analyses based on non-linear fracture mechanics. The structural behaviour could be predicted with good agreement with FEM using both bi-linear and multi-linear stress-crack opening (-w) relationships. When comparing peak loads obtained in the experiments with results from the analyses, the agreement was good. The crack spacing from the experiments was predicted with good agreement using both the analytical approach by Löfgren and the multi-linear FE approach.
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| 24. |
- Jansson, Anette M, 1963, et al.
(author)
-
MATERIAL TESTING AND STRUCTURAL ANALYSIS OF FRC BEAMS - AFRACTURE MECHANICS APPROACH
- 2008
-
In: Conference proceedings - Befib, Chennai India, Sept 2008.
-
Conference paper (peer-reviewed)abstract
- AbstractThe presented work has been focused on strain-softening FRC and the interrelationshipbetween material properties and structural behaviour. The main purpose of this work was toestablish a procedure for structural analysis of flexural members with a combination of steelfibres and conventional reinforcement. A systematic approach for material testing andstructural analysis, based on fracture mechanics, has been used and this covers: (1) materialtesting; (2) inverse analysis; (3) adjustment of the s-w relationship for fibre efficiency; and(4) cross-sectional and structural analysis. The results suggest that the approach used for thematerial testing provides the necessary properties to perform analyses based on non-linearfracture mechanics. The structural behaviour could be predicted with good agreement withFEM using both bi-linear and multi-linear s-w relationships. When comparing the peak loadsobtained in the experiments with the results from the analyses, the agreement was good, witha high correlation. This demonstrates the strength of the fracture-mechanics approach formaterial testing and structural analysis.
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| 25. |
- Karlsson, Mats, 1953, et al.
(author)
-
Methodology for selection of production method in an early stage - improved conceptual design process
- 2017
-
In: IABSE Conference, Vancouver 2017: Engineering the Future - Report. ; 109, s. 1879-1886
-
Conference paper (peer-reviewed)abstract
- The design of buildings and load carrying structures in early stages is a challenging task for a number ofreasons; scant information generally exists and several different requirements involving building structuresshould be managed, including technical, environmental and financial requirements. However, this phase ofthe design process is important and will fundamentally influence the following construction phase, as wellas the entire life of building structures. It is particularly important that the construction phase is properlyconsidered already in the design phase and that the production method selected is suitable for the designof building structures. The purpose of this research has been to improve the design process in theconceptual phase. The findings will highlight the benefits of design for production in bridge engineering.The aim has been to identify examples of practices and work methodologies that are of good caliber in theSwedish bridge construction sector. Early findings show that there exists a divergence between researchfindings and current practices. The research community has presented several participatory methodologiesfor the design process, such as Early Contractor Involvement (ECI) and Integrated Project Delivery (IPD) forthe potential of improving effectiveness in bridge engineering. However, studies of current practices inindustry show that these methodologies are difficult to implement and that there are hiddenconsequences. The processes developed should manage several requirements simultaneously, includingtechnical, environmental, health and safety, and financial. Competencies involved include StructuralEngineering, Architecture and Production Management, in addition to expertise in health and safety,materials science, environmental impact and procurement. Further, the intention is for the processes todeal with verification methods for the proposed conceptual solutions and risk analyses based on qualityassurance. Both new and existing building structures should be considered.
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| 26. |
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| 27. |
- Lövgren, Ingemar, 1972, et al.
(author)
-
In-situ Concrete Building - important aspects of industrialised construction
- 2001
-
In: Nordic Concrete Research. - 0800-6377. ; 26:1, s. 61-81
-
Journal article (peer-reviewed)abstract
- In the ongoing research programme at Chalmers University of Technology, principles and methods for industrialised building with in-situ cast concrete are investigated. The goal is to increase the understanding of, and to develop methods and systems for, industrial building/construction. Improvement of in-situ concrete construction is necessary; partly in order to meet challenges from other materials. The article deals with questions of how the development should proceed and which research disciplines are needed as support. Opportunities for improvement are identified and a framework for the continuing work has been formulated.
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| 28. |
- Lövgren, Ingemar, 1972, et al.
(author)
-
In-situ concrete building - Innovations in Formwork
- 2001
-
In: the 1st International Conference on Innovation in Architecture, Engineering and Construction / Anumba, C.J. , et al.. - 1897911238 ; 1, s. 93-104
-
Conference paper (peer-reviewed)
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| 29. |
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| 30. |
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| 31. |
- Nyström, Ulrika, 1981, et al.
(author)
-
Comparative numerical studies of projectile impacts on plain and steel-fibre reinforced concrete
- 2011
-
In: International Journal of Impact Engineering. - : Elsevier BV. - 0734-743X. ; 38:2-3, s. 95-105
-
Journal article (peer-reviewed)abstract
- The enhanced energy absorption characteristics of fibre-reinforced concrete, compared to plain concrete, has in experimentally studies been shown to improve the projectile resistance and motivate its increased usage in protective structures. However, the high cost of undertaking experiments and the high parameter variation and dependency of the experimental setups and results, respectively, make it difficult to draw generic conclusions of how the addition and increased amount of fibres affects the local damage caused by projectile impact, which motivates the use of numerical simulations to study this. The numerical hydrocode AUTODYN was used in a qualitative study of how the addition of different amounts of fibres, modelled as different post-crack relations, influence the depth of penetration and crater formation on the front and rear face of a concrete target. Fibres added to the concrete mix had a minor influence on the depth of penetration while the crater size on both front and rear faces of the target decreases. The crack propagation beyond the crater on the front face was also reduced when fibres were added to the concrete. An increased amount of fibres in the concrete showed no effect on the size of the front-face crater, but led to further decreased size of the crater on the rear face of the concrete cylinder. It is concluded that the scabbing crater can be reduced in size and prevented by usage of fibre-reinforced concrete even if the depth of penetration is only slightly less than to penetration depth in plain concrete.
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| 32. |
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| 33. |
- Nyström, Ulrika, 1981, et al.
(author)
-
Numerical studies of the combined effects of blast and fragment loading
- 2009
-
In: International Journal of Impact Engineering. - : Elsevier BV. - 0734-743X. ; 36:8, s. 995-1005
-
Journal article (peer-reviewed)abstract
- The well-known synergetic effect of blast and fragment loading, observed in numerous experiments, is often pointed out in design manuals for protective structures. However, since this synergetic effect is not well understood it is often not taken into account, or is treated in a very simplified manner in the design process itself. A numerical-simulation tool has been used to further study the combined blast and fragment loading effects on a reinforced concrete wall. Simulations of the response of a wall strip subjected to blast loading, fragment loading, and combined blast and fragment loading were conducted and the results were compared. Most damage caused by the impact of fragments occurred within the first 0.2 ms after fragments' arrival, and in the case of fragment loading (both alone and combined with blast) the number of flexural cracks formed was larger than in the case of blast loading alone. The overall damage of the wall strip subjected to combined loading was more severe than if adding the damages caused by blast and fragment loading treated separately, which also indicates the synergetic effect of the combined loading. (C) 2009 Elsevier Ltd. All rights reserved.
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| 34. |
- Nyström, Ulrika, 1981, et al.
(author)
-
Simulations of blast and fragment impacts on reinforced concrete
- 2008
-
In: Proceedings of Military Aspects of Blast and Shock, Oslo, Norway 2008.
-
Conference paper (peer-reviewed)abstract
- The complex phenomena involved in combined blast and fragment loading and thesubsequent response of the loaded structure are the main reasons for the limited knowledgewithin this area.In order to increase the knowledge of the effects of combined blast and fragment loading of areinforced concrete beam, numerical simulations were conducted in the hydrocode ANSYSAUTODYN 3D. Since simulations of blast and fragment loading may place different, andsometimes conflicting, demands on the numerical model, the study presented in this paperwas preceded by the work of calibrating and validating the numerical model. This preliminarywork is briefly described.A few cracks to which the elongation of the rear face of the beam was localized were formedin the case of blast loading alone, while the number of flexural cracks in the cases wherefragments were involved was numerous. The increased number of flexural cracks in the casesof fragment impacts may affect the energy-absorbing capacity positively.In the simulations involving fragment impacts the damage also consisted of local damage, i.e.craters on the front face of the beam, scabbing cracks at the rear of the beam, and direct shearcracks close to the supports. Since most damage caused by the fragment impacts occurredvery early in the response (within 0.25 ms), the fragment impacts may have highly influencedthe response in the case of combined loading since the load-carrying capacity of the beammay have been seriously decreased.It can be concluded that the damage caused by combined blast and fragment loading wasmore severe than if adding the damages caused by the blast and fragment loading treatedseparately, indicating a synergy effect in combined loading.
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| 35. |
- Nyström, Ulrika, 1981, et al.
(author)
-
Stötvågs- och splitterbelastade betongkonstruktioner
- 2008
-
In: Bygg&Teknik. - 0281-658X. ; 08:7, s. 46-49
-
Journal article (other academic/artistic)abstract
- Vare sig det handlar om olyckshändelser, terroristattacker eller krigshandlingar finns risken att byggnader i samhället utsätts för explosioner. Huruvida hänsyn tas till detta vid dimensionering och analys av en byggnad beror bland annat på hur stor risken är för att en sådan last ska uppkomma samt hur stor skada denna kan tillåtas orsaka på byggnaden, dess inventarier och på personer i eller i närheten av byggnaden. Att responsen för en struktur utsatt för en extrem dynamisk belastning skiljer sig från responen vid en statisk belastning är känt, men det finns fortfarande mycket att utforska och lära om de fenomen i betongen som kopplas till den extrema belastningen och som leder till denna beteendeskillnad.
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| 36. |
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| 37. |
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| 38. |
- Plos, Mario, 1963, et al.
(author)
-
Evaluering av bärförmåga hos broar med hjälp av förfinade analysmetoder
- 2004
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Reports (other academic/artistic)abstract
- In this project, enhanced methods of analysis were used to demonstrate how higher load carrying capacities can be proven through detailed assessment of bridges in the Swedish road network. Probabilistic analysis, finite element (FE) analysis and alternative design methods, and combinations of these, were described and used together with results from previously performed measurements. The focus of the project has been the application on prestressed concrete box girder bridges. Two bridges owned by the Swedish National Road Administration (Vägverket) were used as case studies: The Källösund Bridge, built with the free cantilevering method as a part of the Tjörn Bridge connection on the west coast of Sweden, and a continuous three-span bridge at a traffic interchange in Kropp close to Helsingborg in the south of Sweden.An assessment strategy for enhanced evaluation of the load carrying capacity of existing bridges is proposed. As a basis for such an evaluation, an initial structural assessment according to current practice should be performed, but with higher demands on a detailed documentation. The enhanced evaluation should thereafter be made step by step and as an integrated part of the decision process. The detailed assessment involves more advanced analysis and judgement, that are not ruled by the detailed regulations and code of practice used in common structural assessment. However, it should have the same aim, intention and safety requirements. It can be based on research results and more enhanced methods for determination of the capacity, and more advanced analysis models of the bridge can be used together with bridge-specific load and material data. Calculations and analyses are made in a continuous interaction with physical investigations of the condition of the bridge, and decisions whether to proceed with the assessment are made successively.For the Källösund Bridge, the evaluation made showed that the load carrying capacity with respect to bending moments was sufficient for a vehicle bogie load of 210 kN according to the Swedish code for road bridge assessment, see Vägverket (1998). However, the capacity with respect to shear and torsion was too small for the same load level, with the existing shear reinforcement. This was still the case when load effects determined through probabilistic evaluation were used, even though they were found to be 9% lower than the load effects determined from the deterministic code loads. An evaluation based solely on the Swedish concrete code, BBK 94 (1994), gives sufficient safety in the latter case, but, on the other hand, the other methods used (EC 2-1 and the modified compression field theory) give a too low capacity. A FE analysis performed resulted in sufficient load carrying capacity for the critical load case with respect to shear and torsion, but non-linear FE analysis of shear failures need to be studied further before the results of such an analysis can be fully adopted.Strengthening of the Källösund Bridge is, based on the evaluation performed, considered to be the safest alternative. In case of further evaluation, an interesting alternative would be to leave the bridge unstrengthened and to expose it to a test loading with successively increasing vehicle loads up to the maximum load level the bridge has been exposed to earlier. Relevant strains, deformations and possibly the support reactions could be measured in order to check if the analysis models used correctly reflects the response of the bridge. Furthermore, a confirmation of the minimum load carrying capacity would be obtained. The response would be followed during the loading and the load increase be terminated if risk of damage or cracking of the webs arises. Regarding the risk of cracking due to shear at the flange to web connection, the study showed that the bridge has sufficient resistance if the classification with respect to environmental influence is reconsidered.For the bridge at Kropp, the evaluation showed that the load A/B, i.e. the axle and bogie loads according to Vägverket (1998), can be raised from 150/255 kN to about 275/630 kN, if certain assumptions were made regarding the dynamic amplification factor and the accuracy of the traffic load. The reasonableness of these assumptions needs to be further evaluated.Further research and development are needed regarding quantification of uncertainties in the modelling of material parameters, loads and structural capacity.
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| 42. |
- Plos, Mario, 1963, et al.
(author)
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Nonlinear FE Analyses of RC Bridge Frame Corners, Based on Fracture Mechanics
- 1998
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In: Journal of Bridge Engineering. - 1084-0702. ; 3:4, s. 204-209
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Journal article (peer-reviewed)abstract
- Reinforced concrete frame corners were analyzed using the nonlinear finite-element method and fracture mechanics. The objective of the study was to determine whether the reinforcement detailing in frame bridges could be simplified, with preserved structural safety, by splicing the reinforcement within the frame corner. A constitutive model for concrete, based on nonlinear fracture mechanics and plasticity, was used. An interface model was used to account for slip between the reinforcement and surrounding concrete. Analysis of previously tested frame specimens, with both spliced and unspliced corner reinforcement, was used to study the overall behavior of the frames; more detailed analysis of only the frame corner regions was used to study the influence of the reinforcement splices. The analyses were found to reflect the mechanical behavior of the specimens, and are in good agreement with the test results. The analysis results support, together with the test results, the idea that it would be feasible to splice all reinforcement in a portal frame bridge within the corner regions.
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| 44. |
- Plos, Mario, 1963, et al.
(author)
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Structural assessment of a prestressed box girder concrete bridge, using non-linear finite element analysis
- 2004
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In: Proceedings of the second international conference on Bridge Maintenance, Safety and Management. - 9058096807 ; , s. 837-838
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Conference paper (peer-reviewed)abstract
- In this study, it was demonstrated how higher load carrying capacity with respect to shear and torsion can be shown for road bridges through non-linear finite element (FE) analyses. A prestressed box girder bridge, the Källösund Bridge, was evaluated as a case study. The Källösund bridge is a 45 years old, cast-in-situ concrete bridge with four spans, constructed with the free cantilevering method on the west coast of Sweden. The case study indicates a substantially higher load carrying capacity for combined shear and torsion, compared to bridge assessment with conventional design methods. In the non-linear analyses of the Källösund bridge, about 40% higher design bogie load than in the initial structural assessment was reached (B = 250 kN), together with the other design loads in ULS, before a shear failure developed for the studied critical load case. With improvements to the model and with deformation controlled loading, an even higher failure load is likely to be shown. However, non-linear analyses of shear failures in this kind of concrete structures are quite rare, and need to be studied further. Furthermore, the analyses performed need to be complemented for other possible critical sections, and for alternative critical load cases.
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| 45. |
- Plos, Mario, 1963, et al.
(author)
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Structural assessment of concrete bridges
- 2007
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In: Nordic Concrete Research. - 0800-6377. ; 30:2, s. 89-102
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Journal article (peer-reviewed)abstract
- The paper summarises the work on concrete bridges performed in the EU project Sustainable Bridges. The work provides enhanced assessment methods that are able to prove higher load-carrying capacities and longer fatigue lives for existing concrete railway bridges, and is implemented in a Guideline [1]. Methods for determination of in-situ material properties and advanced methods for structural analysis were developed. One main focus was non-linear analysis, since these provides the greatest potential for discovering of additional sources for load-carrying capacity. Furthermore, methods to assess the remaining structural resistance of deteriorated concrete bridges with respect to corrosion and fatigue were developed.
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| 46. |
- Plos, Mario, 1963, et al.
(author)
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Structural assessment of concrete bridges
- 2008
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In: Nordic Concrete Research. - 0800-6377. ; 38:2008/2, s. 89-101
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Journal article (peer-reviewed)abstract
- The paper summarises the work on concrete bridges performed in the EU project Sustainable Bridges. The work provides enhanced assessment methods that are able to prove higher load-carrying capacities and longer fatigue lives for existing concrete railway bridges, and is implemented in a Guideline [1]. Methods for determination of in-situ material properties and advanced methods for structural analysis were developed. One main focus was non-linear analysis, since these provides the greatest potential for discovering of additional sources for load-carrying capacity. Furthermore, methods to assess the remaining structural resistance of deteriorated concrete bridges with respect to corrosion and fatigue were developed.
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| 47. |
- Plos, Mario, 1963, et al.
(author)
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Structural assessment of concrete railway bridges
- 2008
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In: Bridge Maintenance, Safety, Management, Healt Monitoring and Informatics. - 9780415468442 ; , s. 705-
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Conference paper (peer-reviewed)abstract
- The work presented provides enhanced assessment methods that are able to prove higher load-carrying capacities and longer fatigue lives for existing concrete railway bridges. It was performed as a part of the EU-project Sustainable Bridges. The results are implemented in the Guideline for Load and Resistance Assessment of existing European Railway Bridges, see SB-LRA (2007) and are reported in detail in a background document, see SB4.5 (2007). The work presents improved methods for the determination of in-situ material properties, for deterministic as well as probabilistic assessments. Advanced methods for structural analysis are presented, e.g. regarding combined shear, torsion and bending interaction. Recommendations are given regarding redistribution of sectional moments and forces obtained from linear finite element analysis. One main objective was to facilitate the use of non-linear analysis for structural assessment. This provides the greatest potential to discover any additional sources for load-carrying capacity, and gives a better understanding of the structural response. Another main objective was to provide methods to assess the remaining structural resistance of deteriorated concrete bridges. Recommendations are given on the effect of corrosion and a methodology is presented for assessment of remaining fatigue life, with emphasis on short-span bridges and secondary elements.
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| 48. |
- Plos, Mario, 1963, et al.
(author)
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Structural Assessment of concrete railway bridges
- 2007
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In: Sustainable Bridges: Assessment for Future Traffic Demands and Longer Lives. - 9788371251610 ; , s. 251-260
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Conference paper (peer-reviewed)abstract
- The aim of the work presented here was to provide enhanced assessment methods that are able to prove higher load carrying capacities and longer service lives for existing concrete railway bridges. One main objective was to develop methods for non-linear analysis since this provides the greatest potential to discover any additional sources for load carrying capacity, and gives an improved understanding of the structural response. Another main objective was to provide methods for assessing deteriorated concrete bridge. Recommendations are given regarding the effect of reinforcement corrosion, particularly on anchorage capacity. Furthermore, a methodology for improved assessment of the remaining fatigue life of short-span concrete bridges and secondary elements is presented. Other topics treated are evaluation of material properties, simplified methods for structural analysis and the bending-shear-torsion interaction.
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| 49. |
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| 50. |
- Plos, Mario, 1963, et al.
(author)
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Structural Assessment using Non-linear Finite Element Analysis: Evaluation of the Shear Capacity for the Källösund Bridge
- 2005
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In: Nordic Concrete Research. Proceedings Nordic Concrete Research Meeting 2005, Sandefjord, Norway. ; , s. 290-292
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Conference paper (peer-reviewed)abstract
- It is demonstrated how higher load carrying capacity with respect to combined shear and torsion can be determined by non-linear finite element (FE) analyses of bridges. The Källösund Bridge, a prestressed concrete box girder bridge on the west coast of Sweden, was evaluated. The bridge is a 45-year-old, cast in situ concrete bridge with four spans, constructed by the free cantilevering method. The case study presented indicates a substantially higher load carrying capacity than for bridge assessment by conventional design methods. About 40% higher design bogie load was reached (B = 250 kN) using non-linear analyses, before a shear failure developed.
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