| 1. |
- Dahlblom, Ola, 1956, et al.
(författare)
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Strukturmekanik - modellering och analys
- 2010
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Strukturmekanik är den del av fysiken som beskriver hur olika material, som formats och sammanfogats till strukturer, bär sina laster. Kunskapen om dessa strukturers verkningssätt kan användas i en skapande process där hållbara och effektiva, funktionella och uttrycksfulla byggnadsverk utformas. Den här läroboken i strukturmekanik baseras på finita elementmetodens metodik. Förståelsen för strukturmekaniska grundelement, fjädrar, stänger, balkar och fundament, byggs successivt upp i en, två och tre dimensioner. Med hjälp av dessa element visas hur komplexa bärande konstruktioner kan modelleras och analyseras. Metoder för såväl linjär som geometriskt och materiellt ickelinjär analys presenteras. För att synliggöra den beskrivna metodikens generalitet finns ett kort avsnitt som tar upp andra områden inom tillämpad mekanik som värmeledning och elektrisk strömning. Läroboken stödjer tre centrala lärandemål: • Kunskap i grundläggande strukturmekanisk teori. • Färdighet i att modellera och analysera strukturer. • Förmåga att i en designprocess värdera och effektivisera föreslagna konstruktionsutformningar.Läroboken vänder sig till civilingenjörsstudenter på kandidatnivå och till högskoleingenjörsstudenter. Datorprogram som stöder bokens framställning finns att fritt ladda ner från hemsidan www.studentlitteratur.se/strukturmekanik.
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| 2. |
- Dahlblom, Ola, et al.
(författare)
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Strukturmekanik - Modellering och analys av ramar och fackverk
- 2010
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Strukturmekanik är den del av fysiken som beskriver hur olika material, som formats och sammanfogats till strukturer, bär sina laster. Kunskapen om dessa strukturers verkningssätt kan användas i en skapande process där hållbara och effektiva, funktionella och uttrycksfulla byggnadsverk utformas. Den här läroboken i strukturmekanik baseras på finita elementmetodens metodik. Förståelsen för strukturmekaniska grundelement, fjädrar, stänger, balkar och fundament, byggs successivt upp i en, två och tre dimensioner. Med hjälp av dessa element visas hur komplexa bärande konstruktioner kan modelleras och analyseras. Metoder för såväl linjär som geometriskt och materiellt ickelinjär analys presenteras. För att synliggöra den beskrivna metodikens generalitet finns ett kort avsnitt som tar upp andra områden inom tillämpad mekanik som värmeledning och elektrisk strömning. Läroboken stödjer tre centrala lärandemål: • Kunskap i grundläggande strukturmekanisk teori. • Färdighet i att modellera och analysera strukturer. • Förmåga att i en designprocess värdera och effektivisera föreslagna konstruktionsutformningar. Läroboken vänder sig till civilingenjörsstudenter på kandidatnivå och till högskoleingenjörsstudenter. Datorprogram som stöder bokens framställning finns att fritt ladda ner från hemsidan www.studentlitteratur.se/strukturmekanik.
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| 3. |
- Lundstedt, Karin, 1963-
(författare)
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Thermal stresses in load-bearing glass-timber components
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermal stresses can arise in glass used in architectonic realisations in buildings as a result of solar irradiation: that is, sunlight. The magnitude of these thermal stresses depends on the temperature conditions in the glass in terms of the temperature differences between warm and cold areas. The work described here has verified the existence and distribution of thermal stresses in glass, both theoretically and experimentally, in a load-bearing element made of glass and wood, when exposed to incident solar radiation and various degrees of shading. The finite element method was used in order to simulate the temperature distribution in the glass, together with the resulting associated thermal stresses. Parts of these model results were then compared with results and data from experimental investigations in a solar simulator. The experimental trials were carried out on a plain glass sheet and on a wood-framed glass sheet. This frame assembly saw the glass fitted in a wooden frame such that its edge was flush with the edges of the frame and therefore freely exposed to the surroundings. Two different grades of glass were analysed in the theoretical modelling and used in the experimental solar exposure: a clear glass, with a low absorption coefficient, and a tinted glass having a relatively high absorption coefficient. The experimental part of the work included two different finishes to the glass edge: as-cut, with no further attention, and cut and smoothed. The results from the finite element method calculations agree relatively well with the experimental results. When simulating the temperature values and distributions, the value of the coefficient of heat transfer is an important factor in determining the results. The coefficient can be given either a constant value, taken from a standard, or a calculated value that varies depending on the surface temperature and ambient temperature at every instant. For the clear glass with a low coefficient of absorption, the calculated temperatures did not differ significantly depending on which method had been used to provide a value for the coefficient of heat transfer. However, for the glass with a high coefficient of absorption, and when exposed to high solar intensity, a calculated value of coefficient of heat transfer should be used in order to arrive at relevant values of surface temperatures and stresses. Thermal tensile stresses have more effect on the total stress level than have stresses arising from typical in-service vertical loads.
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| 4. |
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| 5. |
- Obaidat, Yasmeen, et al.
(författare)
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Plate end debonding : a modified approach to predict stress in FRP–concrete bond
- 2012
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Ingår i: Proceedings: IIFC Official Conferences: FRP Composites in Construction (CICE) Series.
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Konferensbidrag (refereegranskat)abstract
- An important failure mode of RC beams retrofitted with FRP plates is plate end debonding. Design codes provide equations for estimating shear stress at the plate end, but none of these equations include the FRP to concrete width ratio. This paper suggests an improved equation for calculating shear stress that includes the width ratio. The new equation was obtained by fitting 3D nonlinear FEM results to a proposed relation and provided a clearly improved prediction of the shear stress. The simulations also showed that a large width ratio and an adhesive of low stiffness decrease the risk of debonding.
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| 6. |
- Obaidat, Yasmeen, et al.
(författare)
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Retrofitting of reinforced concrete beams using composite laminates
- 2011
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 25:2, s. 591-597
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Forskningsöversikt (refereegranskat)abstract
- This paper presents the results of an experimental study to investigate the behaviour of structurally damaged full-scale reinforced concrete beams retrofitted with CFRP laminates in shear or in flexure. The main variables considered were the internal reinforcement ratio, position of retrofitting and the length of CFRP. The experimental results, generally, indicate that beams retrofitted in shear and flexure by using CFRP laminates are structurally efficient and are restored to stiffness and strength values nearly equal to or greater than those of the control beams. It was found that the efficiency of the strengthening technique by CFRP in flexure varied depending on the length. The main failure mode in the experimental work was plate debonding in retrofitted beams. (C) 2010 Elsevier Ltd. All rights reserved.
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| 7. |
- Obaidat, Yasmeen Taleb, et al.
(författare)
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Evaluation of Parameters of Bond Action between FRP and Concrete
- 2013
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Ingår i: Journal of Composites for Construction. - 1090-0268. ; 17:5, s. 626-635
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the evaluation of parameters describing bond action between fiber-reinforced polymer (FRP) and concrete in RC structures strengthened in flexure. The parameters were evaluated on the basis of fitting nonlinear finite-element results to experimental results from literature. Three-dimensional (3D) finite-element simulations were used to account for transversal effects without introducing any geometry-related correction coefficients in the material model. The parameters defining the material model, describing bond action, were initial stiffness, shear strength, and fracture energy of the FRP-concrete interface. Bilinear, trilinear, and exponential curve shapes were evaluated. The parameters were related to concrete tensile strength and shear stiffness of the adhesive. According to the analysis, the models provide a good estimation of ultimate load and strain distribution in FRP compared with test results. The results showed that whether the bond-slip curve was assumed to be bilinear, trilinear, or exponential has a minor effect.
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| 8. |
- Obaidat, Yasmeen, et al.
(författare)
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The effect of CFRP and CFRP/concrete interface models when modelling retrofitted RC beams with FEM
- 2010
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Ingår i: Composite Structures. - : Elsevier BV. - 1879-1085 .- 0263-8223. ; 92:6, s. 1391-1398
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Tidskriftsartikel (refereegranskat)abstract
- Concrete structures retrofitted with fibre reinforced plastic (FRP) applications have become widespread in the last decade due to the economic benefit from it. This paper presents a finite element analysis which is validated against laboratory tests of eight beams. All beams had the same rectangular cross-section geometry and were loaded under four point bending, but differed in the length of the carbon fibre reinforced plastic (CFRP) plate. The commercial numerical analysis tool Abaqus was used, and different material models were evaluated with respect to their ability to describe the behaviour of the beams. Linear elastic isotropic and orthotropic models were used for the CFRP and a perfect bond model and a cohesive bond model was used for the concrete-CFRP interface. A plastic damage model was used for the concrete. The analyses results show good agreement with the experimental data regarding load-displacement response, crack pattern and debonding failure mode when the cohesive bond model is used. The perfect bond model failed to capture the softening behaviour of the beams. There is no significant difference between the elastic isotropic and orthotropic models for the CFRP. (C) 2009 Elsevier Ltd. All rights reserved.
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| 9. |
- Ormarsson, Sigurdur, 1963-, et al.
(författare)
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An extended beam model for simulation of hygro-mechanical and visco elastic deformations in inhomogeneous timber structures
- 2014
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Ingår i: 11th World Congress on Computational Mechanics - 2014. - Barcelona : Spanish Association for Numerical Methods in Engineering.
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Konferensbidrag (refereegranskat)abstract
- Due to numbers of failures of large glue laminated (glulam) timber structures there seems to be a need for better design tools for wood applications. In EC5 and in many textbooks on timber design it is stated that the moisture sensitivity of the wood material needs to be taken into account in the design process. But the fact is that in stress calculations associated with ordinary timber design, these matters are not dealt with properly. The problem is that it is very difficult to predict the variation of moisture-related stresses during the service life of the timber structure as a whole. A proper prediction requires that material inhomogeneity, mechano-sorption effect and visco-elastic behaviour are taken into account. The paper presents a finite element implementation of a new beam element able to simulate hygro-mechanical and visco-elastic behaviours in inhomogeneous timber structures.
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| 10. |
- Ormarsson, Sigurdur, 1963-, et al.
(författare)
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Finite element modelling of moisture related and visco-elasticdeformations in inhomogeneous timber beams
- 2013
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Ingår i: Engineering structures. - : Elsevier. - 0141-0296 .- 1873-7323. ; 49, s. 182-189
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Tidskriftsartikel (refereegranskat)abstract
- Wood is a hygro-mechanical, non-isotropic and inhomogeneous material concerning both modulus ofelasticity (MOE) and shrinkage properties. In stress calculations associated with ordinary timber design,these matters are often not dealt with properly. The main reason for this is that stress distributions ininhomogeneous glued laminated members (glulam) and in composite beams exposed to combinedmechanical action and variable climate conditions are extremely difficult to predict by hand. Severalexperimental studies of Norway spruce have shown that the longitudinal modulus of elasticity and thelongitudinal shrinkage coefficient vary considerably from pith to bark. The question is how much thesevariations affect the stress distribution in wooden structures exposed to variable moisture climate. Thepaper presents a finite element implementation of a beam element with the aim of studying how woodencomposites behave during both mechanical and environmental load action. The beam element is exposedto both axial and lateral deformation. The material model employed concerns the elastic, shrinkage, mechano-sorption and visco-elastic behaviour of the wood material. It is used here to simulate the behaviourof several simply-supported and continuous composite beams subjected to both mechanical and environmentalloading to illustrate the advantages this can provide. The results indicate clearly both the inhomogeneityof the material and the variable moisture action occurring to have had a significant effecton the stress distribution within the cross-section of the products that were studied.
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