| 1. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Industrial bridge building- An effective bridge construction process through an integrated design and construction process
- 2014
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Ingår i: Nordic Concrete Research. - 0800-6377. - 9788282080439 ; 2014:2, s. 79-82
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Konferensbidrag (refereegranskat)abstract
- This PhD-project aims to develop and industrialise bridge building, in order to achieve a more efficient and sustainable bridge construction process. The advancements of several key areas - materials science and technology, design and analysis methods, production techniques and information and communication technology - have resulted in a vast potential to rationalise the process and renew the designer's role. Initially, the project will define effective bridge construction criteria’s by means of interviews and case-studies. The work should result in an integrated design and production process. This project is a collaborative project, involving: Swedish Transport Administration, WSP and Chalmers.
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| 2. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Samarbetsprojekt för effektivare brobyggande
- 2014
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Ingår i: Bygg & Teknik. - 0281-658X. ; 2014:7, s. 58-61
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Den svenska anläggningsbranschen har i ett flertal utredningar fått skarp kritik på grund av dålig produktivitet. Forskning visar på samma tendenser i övriga Europa och USA. Vissa mätningar tyder på att byggandet i den svenska anläggningsbranschen har en kostnadsökning som är dubbelt så hög jämfört med övriga branscher under de senaste 20 åren. Låg produktivitet och låg innovationsförmåga i byggbranschen leder till högre kostnader som inte garanterat ger en högre kvalitet. Trenden behöver vändas så att avkastningen på investeringar i vår infrastruktur ökar! Det första steget är att integrera konstruktions- och produktionsprocesserna, vilket ger kortare ledtider för både planering och uppförande av byggnadsverk. Onödigt långa byggtider orsakar störningar för andra aktörer i samhället.I ett pågående doktorandprojekt, som är ett samarbete mellan Trafikverket, WSP och Chalmers, söks möjligheten till att öka produktiviteten inom den svenska anläggningsbranschen. Huvudspåret är att utveckla och industrialisera brobyggandet. En effektivare byggindustri skapar möjligheter till att generera ett mervärde för samhället där mervärdet exempelvis kan motsvaras av att konstruktioner byggs med högre kvalitet till samma kostnad som idag alternativt samma eller högre kvalitet till en lägre kostnad än idag. Bortsett från rena kostnader bör naturligtvis en effektivare byggindustri också se till att lösningar väljs utifrån ett hållbart samhälle men med bibehållen fokus på produktivitet och innovation. En sådan lösning kan variera från själva processen till konstruktionsdetaljer.
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| 3. |
- Ekström, Jonas, 1985, et al.
(författare)
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Influence of strain softening on spalling of concrete due to blast load
- 2014
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Ingår i: Nordic Concrete Research. ; 2/2014:50
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Konferensbidrag (refereegranskat)abstract
- A society needs a certain readiness for different emergency situations, such as explosions within the urban community but also civil safety shelter in the case of war. Therefore, the ability to evaluate and to strengthen existing buildings exposed to new demands is of great importance. Many experiments and numerical analyses indicate that structures of fibre reinforced concrete yield a more favourable response during dynamic load conditions compared to plain concrete. In this study the effects of spalling of a concrete wall subjected to blast loads were studied for plain concrete modelled with an elastic-plastic material model. The results from the analysis show that spalling occur when cyclic loading from a pressure wave gradually increase the plastic strains in the concrete.
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| 4. |
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| 5. |
- Fall, David, 1983, et al.
(författare)
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Modelling cracking and bending failure of SFRC beams with conventional reinforcement
- 2013
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Ingår i: 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures. - 9788494100413 ; , s. 1276-1285
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Konferensbidrag (refereegranskat)abstract
- In this study three beams, with varying contents of steel fibre reinforcement, were tested in four point bending and compared with results from FE-analysis. The beams were part of a larger experimental programme where relevant material properties were investigated. FE-modelling was performed using a two dimensional model. Concrete was represented by four-node quadrilateral isoperimetric plane stress elements. The smeared crack approach was utilized and the stress-strain relation describing the tensile behavior of the concrete was calculated from uni-axial test results, assuming the crack bandwidth to be equal to the element length. In compression, the concrete was assumed to behave elasto ideal-plastic. The reinforcement was modelled by straight 2-node truss elements connected to the concrete by two-dimensional interface elements providing the bond-slip properties. A material model including hardening effects was derived from tension tests of reinforcement bars and used for modelling the conventional reinforcement. A multi-linear bond-slip model was established through pull-out tests. As an alternative, analyses were also performed taking into account a reduction of the bond stress after yielding of the reinforcement occurred. Loading was applied in two phases: the first comprehending only the self-weight, while incremental loading was applied by deformation control during the second phase. General agreement between experiments and FE-analyses was obtained with regard to load-displacement behaviour. By observing the crack patterns, both from FE-analysis and experiments, it can be concluded that the general behaviour agreed; however, in the analyses not all cracks were fully localized. A higher degree of crack localization was obtained when the bond loss at yielding was included.
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| 6. |
- Fall, David, 1983, et al.
(författare)
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Non-linear Finite Element Analysis of Steel Fibre Reinforced Beams with Conventional Reinforcement
- 2012
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Ingår i: 8th RILEM International Symposium on Fiber Reinforced Concrete: challenges and opportunities (BEFIB 2012). - 9782351581322 ; , s. 1033-1045
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Konferensbidrag (refereegranskat)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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| 7. |
- Fall, David, 1983, et al.
(författare)
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Reinforcing tailor-made concrete structures: Alternatives and challenges
- 2012
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Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 44, s. 372-378
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Tidskriftsartikel (refereegranskat)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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| 8. |
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| 9. |
- Fall, David, 1983, et al.
(författare)
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Two-way slabs: Experimental investigation of load redistributions in steel fibre reinforced concrete
- 2014
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Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 80, s. 61-74
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Tidskriftsartikel (refereegranskat)abstract
- In the design of two-way reinforced concrete slabs, e.g. using the strip or yield line design method, the possibility of redistributing the load between different loading directions is used. The main aim of the present study was to investigate how fibres affect the structural behaviour such as the possibility for redistribution, crack patterns and load-carrying capacity. The investigation was conducted by means of experiments on two-way octagonal slabs, simply supported on four edges, centrically loaded with a point load. The slabs spanned 2.2 m in both directions and the reinforcement amount was twice as large in one direction as in the other, in order to provoke uneven load distribution. Three slabs of each reinforcementconfiguration were produced and tested: conventionally reinforced slabs, steel fibre reinforced slabs and a combination of both reinforcement types. The reaction force on each supported edge was measured on five rollers per edge. A moderate fibre content (35 kg/m3) of double hook-end steel fibres was used. The steel fibres affected the structural behaviour significantly by providing post-cracking ductility and by increasing the ultimate load-carrying capacity by approximately 20%. Most significant, the steel fibres influenced the load redistribution in such a way that more load could be transferred to supports in theweaker direction after cracking. Further, more evenly distributed support reactions were obtained in the slabs containing both reinforcement types compared to the case when only conventional reinforcement was used. The slabs reinforced by steel fibres alone did not experience any bending hardening; however, a considerable post-cracking ductility was observed. Furthermore, the work presented in this paper will provide results suitable for use in benchmarking numerical and analytical modelling methodsfor steel fibre reinforced concrete, as the experimental programme also included extensive testing ofmaterial properties.
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| 10. |
- Grassl, Peter, 1974, et al.
(författare)
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A damage-plasticity model for the dynamic failure of concrete
- 2011
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Ingår i: 8th International Conference on Structural Dynamics, Leuven, Belgium.
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Konferensbidrag (refereegranskat)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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