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  • 51.
    Hosseinpourpia, Reza
    et al.
    Islamic Azad University, Iran ; Georg-August University, Germany.
    Varshoee, Ali
    Islamic Azad University, Iran.
    Soltani, Mojtaba
    Islamic Azad University, Iran.
    Hosseini, Payam
    Sharif University of Technology, Iran.
    Ziaei Tabari, Hassan
    Islamic Azad University, Iran.
    Production of waste bio-fiber cement-based composites reinforced with nano-SiO2 particles as a substitute for asbestos cement composites2012In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 31, p. 105-111Article in journal (Refereed)
    Abstract [en]

    The environmental impact of asbestos fibers on human health and their consequent safety-related problems indicate that there is a significant need to replace this material in all asbestos-containing products. Many different types of fibers have been introduced to replace asbestos fibers.

    In this study, the performance of silica nano-particles combined with waste paper pulp fibers (sulfite fibers) has been investigated. Different mechanical (compressive and flexural strengths and bending performance), durability (water absorption), physical (bulk density and flowability), and microstructural (scanning electron microscopy) tests were conducted to examine the properties of manufactured green composites.

    The results reveal that the mechanical properties of cement-based composites containing a ternary system of “natural waste fiber–silica nano-particle cement” have been enhanced. Adding silica nano-particles allows the development of green cement-based composites and movement toward sustainable development in the concrete industry.

  • 52.
    Hu, Min
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Local variation in bending stiffness in structural timber of Norway spruce: for the purpose of strength grading2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Most strength grading machines on the European market use an averagemodulus of elasticity (MOE), estimated on a relatively large distance along awood member, as the indicating property (IP) to bending strength. Theaccuracy of such grading machines in terms of coefficient of determination israther low at R2 ≈ 0.5. This research is motivated by a desire to increase theaccuracy of the strength grading in the industry today. The aim of the presentstudy is to contribute knowledge of local variation in bending stiffness/MOEwith high resolution and thus locate weak sections due to stiffness reducingfeatures (the most important is knots) for structural timber.The present study introduces three methods that involve structural dynamics,classical beam theory and optical measurement to assess local wood stiffness.Specifically:

    • The dynamic method, in which a wood member is treated as an ordinaryphysical structure and the local stiffness is studied by exploring itsdynamic properties.
    • In Method II, a bending MOE profile is established based on local fibre angle information. The local fibre orientation is detected through highresolution laser scanning based on the tracheid effect.
    •  For Method III, a bending MOE profile is established using surfacestrain information under four-point bending. A high resolution strainfield is obtained using the digital image correlation (DIC) technique.

    From the present study, the two latter methods are more favourable inevaluating the local stiffness within a piece of structural timber. Moreover, thestudy reveals that the established bending MOE profiles using the two lattermethods, i.e. based on information of the local fibre angle and surface strain,agree reasonably well. However, for some patterns of knot clusters, the localbending MOE, calculated on the basis of fibre angles, is significantly higherthan the local bending MOE estimated on the basis of surface strain.

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    Licentiate thesis
  • 53.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    SP Tech Res Inst Sweden, SP Wood Technol, Växjö.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Local variation of modulus of elasticity in timber determined on the basis of non-contact deformation  measurement and scanned fibre orientation2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 1, p. 17-27Article in journal (Refereed)
    Abstract [en]

    During the last decade, the utilization of non-contact deformation measurement systems based on digital image correlation (DIC) has increased in wood related research. By measuring deformations with DIC systems, surface strain fields can be calculated. The first aim of this study concerns the possibility to detect detailed strain fields along the entire length of a wooden board subjected to pure bending and the potential of using such strain fields to determine a bending modulus of elasticity (MOE) profile along a board. Displacements were measured over 12 subareas along a flat surface of the board. For each such area, a separate local coordinate system was defined. After the transformation of locally measured coordinates to a global system, high resolution strain fields and a corresponding bending MOE profile were calculated. A second method in establishing bending MOE profiles is to use fibre angle information obtained from laser scanning and a calculation model based on integration of bending stiffness over board cross sections. Such profiles have recently been utilized for accurate strength grading. A second aim of this study was to investigate the accuracy of the bending MOE profiles determined using the latter method involving fibre angle information. Bending MOE profiles determined using the two described methods agree rather well. However, for some patterns of knot clusters, the local bending MOE, calculated on the basis of fibre angles and integration of bending stiffness, is overestimated. Hence, this research adds knowledge that may be utilized to improve the newly suggested strength grading method.

  • 54.
    Håkansson, Annie
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Nilsson, Elin
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Varför växer inte Älmhult?2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Detta examensarbete behandlar varför Älmhult inte växer. De senast tio åren har det rått bostadsbrist i Älmhult, framför allt på hyreslägenheter. Det finns undersökningar som visar att det finns ett hundratal potentiella inflyttare, men ett problem är att det inte finns någonstans att bo. För att ta reda på vad det är som hindrar företag från att bygga nya bostäder har vi intervjuat aktörer och politiker som är aktiva i Älmhults kommun. Intervjuerna har sammanställts och bearbetats i resultatet. Här framkommer bland annat åsikter om problematiken i att det inte är ekonomiskt lönsamt att nyproducera hyreslägenheter.

     

    Studien syftar till att ge en samlad bild över varför det inte byggs mer bostäder i Älmhult och vad man bör arbeta vidare med för att lösa detta problem. Arbetet har framför allt behandlat Älmhult som tätort och inte som kommun.

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  • 55.
    Isaksson, Simon
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Nilsson, Julia
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Svetsad upplagsklack – dimensionering baserad på konstruktörers antaganden2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Hur konstruktörer dimensionerar knutpunkter är olika från konstruktör till konstruktör. Detta gör att knutpunktslösningarna kommer att se något olika ut beroende på vem som dimensionerar. Beroende på hur konstruktionsarbetet delas upp mellan de inblandade konstruktörerna kan samma typ av knutpunkt utformas med olika lösningar, i olika delar av konstruktionen. Detta resulterar i många olika ritningar och mycket extra arbete för de företag som tillverkar ståldetaljer samt montörer. Under examensarbetet har tre konstruktörer intervjuats för att få förståelse för vilka val de ställs inför under dimensioneringen samt hur de genomför sina beräkningar. Utifrån dessa genomfördes beräkningar på upplagsklacken för att studera skillnader i dimensionerna. I examensarbetet beskrivs tillvägagångssättet för beräkning av svets runt en upplagsklack i en pelar-balkinfästning. Med teori och beräkningar som underlag togs ett beräkningshjälpmedel i form av tabeller fram över hur klacken borde dimensioneras. Detta beräkningshjälpmedel är sammanställt för att underlätta och effektivisera arbetet för konstruktörer, tillverkare och montörer genom att ge mer enhetliga upplagsklackar.

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    fulltext
  • 56.
    Ivansson, Patrik
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Werner, Christian
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Bengtsson, Jonas
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Kraftkabelförläggning i mark: - en studie av produktionsmetoder2006Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The assignment given to us by NCC was to compose a degree project based on ground excavations for power cables. The aim of the study was to examine suitable excavation methods depending on different possible terrain conditions. The amount of previously written material within this subject is nearly non- existent and therefore there is a genuine interest by the NCC to receive a compilation of different production methods. The greater part of this study is based upon interviews with several companies active within this area of expertise. The technique of placing the electricity grid beneath ground for safety is today getting more and more common. The aftermath of the hurricane “Gudrun” has forced several power companies to re-evaluate their electric supply network, which has lead to more placements of power cables underground.

    We have come to the conclusion that there are several factors that would affect the method of choice for cable excavations. Costumer demands, obstacles and the difference in ground conditions are vital factors behind the verdict for suitable production methods.

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    FULLTEXT01
  • 57.
    Janz, Marten
    et al.
    Lund University.
    Johannesson, Björn
    Lund University.
    Measurement of the moisture storage capacity using sorption balance and pressure extractors2001In: Journal of Thermal Envelope and Building Science, ISSN 1097-1963, E-ISSN 1530-8073, Vol. 24, no 4, p. 316-334Article in journal (Refereed)
    Abstract [en]

    This paper presents measurements of the moisture storage capacity for several different porous building materials. The storage capacity is measured by a sorption balance in the hygroscopic range and with pressure plate and pressure membrane extractors in the superhygroscopic range. The results are presented both as retention curves and sorption isotherms and indicate, among other things, that some materials have a large hysteresis between absorption and desorption in the superhygroscopic range. This is contrary to what sometimes has been postulated.

  • 58.
    Jensen, Mads Mønster
    et al.
    Technical University of Denmark, Denmark.
    De Weerdt, K.
    Norwegian University of science and Technology, Norway.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Geiker, M. R.
    Norwegian University of science and Technology, Norway.
    Use of a multi-species reactive transport model to simulate chloride ingress in mortar exposed to NaCl solution or sea-water2015In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 105, p. 75-82Article in journal (Refereed)
    Abstract [en]

    Simulations of ion ingress in Portland cement mortar using a multi-species reactive mass transport model are compared with experimental test results. The model is an extended version of the Poisson–Nernst–Planck equations, accounting for chemical equilibrium. Saturated mortar samples were exposed after 8 days of hydration to a NaCl-solution or natural sea-water in a laboratory controlled environment for the experimental part. The samples were analyzed for the total chloride content after 21, 90 and 180 days of exposure, at varying depths from the exposed surface. The applicability of the reactive mass transport model is shown by comparing the simulation and experimental results. The tortuosity factor used in the simulations is adjusted to obtain the best reproduction of the experimental results. The model predicts the total chloride content satisfactorily, despite assumptions in the simulation like fixed hydration degree over time. Improvements and suggestions for further development of the model are discussed, e.g. extended hydration description, improved overall chemical description and a more strict use of the tortuosity factor.

  • 59.
    Jensen, Mads Mønster
    et al.
    Technical University of Denmark, Denmark.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Geiker, Mette Rica
    Norwegian University of Science and Technology, Norway.
    A Numerical Comparison of Ionic Multi-Species Diffusion with and without Sorption Hysteresis for Cement-Based Materials2015In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 107, no 1, p. 27-47Article in journal (Refereed)
    Abstract [en]

    A finite element solution for a mass transport model for porous materials accounting for sorption hysteresis is presented in this paper. The model is prepared for modeling of concrete durability, but the general presentation makes it suitable for other porous materials like soil and tissues. The model is an extended version of the Poisson–Nernst–Planck (PNP) system of equations. The PNP extension includes a two-phase vapor and liquid model coupled by a sorption hysteresis function and a chemical equilibrium term. The strong and weak solutions for the equation system are shown, and a finite element formulation is established by Galerkin’s method. A single-parameter implicit time integration scheme is used for solving the transient response, and the out-of-balance solution is minimized by using a modified Newton–Raphson scheme in which the tangential stiffness is not computed exactly. The sorption hysteresis is added to the solution procedure by a rate function. The hysteresis effect is described by scanning curves defined between two boundary sorption isotherms. A numerical example was constructed to show the applicability and compare a simple approach and a extended approach within the sorption hysteresis model. The examples illustrate the impact of changing relative humidity at the mass transport boundary on the adsorption and desorption stages of a cement-based material. Changes in the pore solution ion concentrations are a result of the changing moisture content, which are shown by the example. Comparing the two approaches showed significant deviations in the liquid content and ion concentrations, in parts of the domain considered.

  • 60.
    Jensen, Mads Mønster
    et al.
    Technical University of Denmark, Denmark.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Geiker, Mette Rica
    Norwegian University of Science and Technology, Norway.
    Framework for reactive mass transport: phase change modeling of concrete by a coupled mass transport and chemical equilibrium model2014In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 92, p. 213-223Article in journal (Refereed)
    Abstract [en]

    Reactive transport modeling is applicable for a range of porous materials. Here the modeling framework is focused on cement-based materials, where ion diffusion and migration are described by the Poisson–Nernst–Planck equation system. A two phase vapor/liquid flow model, with a sorption hysteresis description is coupled to the system. The mass transport is solved by using the finite element method where the chemical equilibrium is solved explicitly by an operator splitting method. The iphreeqc library is used as chemical equilibrium solver. The equation system, solved by iphreeqc, is explained for aqueous, pure phase and solid solution reactions. Numerical examples, with cement-based materials, are constructed to demonstrate transient phase change modeling. A simulation of pure multi-species leaching from the material, showing deterioration of the solid phases is described and calculated. A second simulation, showing multi-species ingress with formation of new solid phases in the domain is described and calculated. It is shown that the numerical solution method is capable of solving the reactive mass transport system for the examples considered.

  • 61.
    Jensen, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Implementering av byggnadsinformationsmodellering i byggproduktionen2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    De större företagen i Sverige använder alltmer byggnadsinformationsmodellering (BIM) i sina byggprojekt. Examensarbetets syfte är att kartlägga i vilken utsträckning BIM påverkar effektiviteten i produktionsfasen på två byggarbetsplatser, Fortnox Arena och Myresjöhus Arena, båda i Växjö. Rapporten belyser BIM, med dess möjligheter respektive svårigheter samt hur det kan användas i produktionsskedet. Utgångspunkten för analysen är intervjuer av olika entreprenörer som medverkade i något av de två nämnda byggprojekten. Intervjuerna visade att BIM tillämpas till viss del på arbetsplatsen och BIM anses bidra till tidsbesparing i projekten. Med hjälp av intervjuerna och teori har analys och diskussion förts kring hur BIM kan användas i produktionen i större utsträckning för att uppnå en ökad effektivitet.

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  • 62.
    Johannesson, Björn
    Lund Institute of Technology.
    A theoretical model describing diffusion of a mixture of different types of ions in pore solution of concrete coupled to moisture transport2003In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 33, no 4, p. 481-488Article in journal (Refereed)
    Abstract [en]

    A theoretical model is established for diffusion of different types of ions in pore solution of concrete and the coupling to moisture flow and moisture content. Mass exchanges between ions in pore solution and solid hydration products in the concrete are also considered. The basic concepts behind the so-called mixture theory are used. The development of a mass balance principle for ions in pore solution is established. This principle accounts for (i) diffusion caused by concentration gradients of ions and gradients of the so-called internal electrical potential, (ii) convection, i.e. the effect on the motion of ions due to a motion of the pore solution in concrete, (iii) the effect on the concentration due to changes in the moisture content, and finally, (iv) the effect of mass exchange of ions between solid hydration products and the bore solution phase. The model is general in the sense that all different types of ions appearing in pore solution phase can-be included and computed for during quite arbitrary boundary conditions.

  • 63.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Comparison between the Gauss' law method and the zero current method to calculate multi-species ionic diffusion in saturated uncharged porous materials2010In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 37, no 5, p. 667-677Article in journal (Refereed)
    Abstract [en]

    There exist, mainly, two different continuum approaches to calculate transient multi species ionic diffusion. One of them is based on explicitly assuming a zero current in the diffusing mixture together with an introduction of a streaming electrical potential in the constitutive equations for the mass density flow of ionic species. The other is based on using the Gauss’ law and assuming no polarization, in order to obtain an equation for the determination of the electrical field, together with adding the electrical field in the constitution of the ionic mass density flows. The important difference of the two types of potentials, that is, the streaming electrical potential and the electrical field is carefully examined. A novel numerical method based on the finite element approach is established for the zero current method case. The proposed numerical method uses the direct calculation of the coupled set of equation in favor of the staggering approach. A one step truly implicit time stepping scheme is adopted together with an implementation of a modified Newton-Raphson iterational scheme for search of equilibrium at each considered time step calculation. Results from the zero current case are compared with existing results from the solutions of the Gauss’ law method. For the studied case the calculated concentrations of the ionic species, using the two different methods, differed very little.

  • 64.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Development of a Generalized Version of the Poisson-Nernst-Planck Equations Using the Hybrid Mixture Theory: Presentation of 2D Numerical Examples2010In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 85, no 2, p. 565-592Article in journal (Refereed)
    Abstract [en]

    A numerical scheme for the transient solution of generalized version of the Poisson-Nernst-Planck equations is presented. The finite element method is used to establish the coupled non-linear matrix system of equations capable of solving the present problem iteratively. The Poisson-Nernst-Planck equations represent a set of diffusion equations for charged species, i.e. dissolved ions. These equations are coupled to the ‘internally’ induced electrical field and to the velocity field of the fluid. The Nernst-Planck equations describing the diffusion of the ionic species and the Gauss’ law in used are, however, coupled in both directions. The governed set of equations is derived from a simplified version of the so-called hybrid mixture theory (HMT). This theory is a special version of the more ‘classical’ continuum mixture theories in the sense that it works with averaged equations at macro-scale and that it includes the volume fractions of phases in its structure. The background to the Poisson-Nernst-Planck equations can by the HMT approach be described by using the postulates of mass conservation of constituents together with the Gauss’ law used together with consistent constitutive laws. The HMT theory includes the constituent forms of the quasi-static version of Maxwell’s equations making it suitable for analyzes of the kind addressed in this work. Within the framework of HTM constitutive equations has been derived using the postulate of entropy inequality together with the technique of identifying properties by Lagrange multipliers. These results will be used in obtaining a closed set of equations for the present problem.

  • 65.
    Johannesson, Björn
    Lund Institute of Technology.
    Diffusion of a mixture of cations and anions dissolved in water1999In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 29, no 8, p. 1261-1270Article in journal (Refereed)
    Abstract [en]

    In service life modeling of concrete, the ion transport in the pore solution is crucial. The main deterioration phenomena associated with ions in the pore solution are (1) corrosion due to external chloride ions reaching the embedded reinforcement bars; (2) carbonation due to presence of dissolved carbon dioxide (which will form carbonic acid with water) supplied from the surrounding air. and (3) leaching of hydroxide ions from the pore solution to the surrounding environment. Models dealing with diffusion of ions are usually based on the mass balance equations for the individual diffusing ions together with constitutive relations for the mass density flows and for the mass exchange among the constituents. The important consequences of electroneutrality among the diffusing ions, however, is often omitted in models dealing with diffusion of ions in the pore solution of concrete. Here a method will be examined that allows diffusion of different ions in water, which satisfies both the electroneutrality requirement and the mass balance laws. For simplicity the effect of built-up electric double layers on the charged pore walls will not be treated.

  • 66.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Dimensional and ice content changes of hardened concrete at different freezing and thawing temperatures2010In: Cement & Concrete Composites, ISSN 0958-9465, E-ISSN 1873-393X, Vol. 32, no 1, p. 73-83Article in journal (Refereed)
    Abstract [en]

    Samples of concrete at different water-to-cement ratios and air contents subjected to freeze/thaw cycles with the lowest temperature at about -80 degrees C are investigated. By adopting a novel technique, a scanning calorimeter is used to obtain data from which the ice contents at different freeze temperatures can be calculated. The length change caused by temperature and ice content changes during test is measured by a separate experiment using the same types of freeze-thaw cycles as in the calorimetric tests. In this way it was possible to compare the amount of formed ice at different temperatures and the corresponding measured length changes. The development of cracks in the material structure was indicated by an ultra-sonic technique by measuring on the samples before and after the freeze-thaw tests. Further the air void structure was investigated using a microscopic technique in which air'bubble' size distributions and the so-called spacing factor, indicating the mean distance between air bubbles, were measured. By analyzing the experimental result, it is concluded that damages occur in the temperature range of about -10 degrees C to -55 degrees C, when the air content is lower than about 4% of the total volume. For a totally water-saturated concrete, damages always occur independently of the use of entrained air or low water-to-cement ratios. It is, further, concluded that the length changes of these samples correspond to the Calculated ice contents at different temperatures in a linear fashion. @ 2009 Elsevier Ltd. All rights reserved.

  • 67.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Freeze/thaw phenomena in concrete at low temperatures2007In: Nordic Concrete Research, 2007Conference paper (Other academic)
    Abstract [en]

    Freeze/thaw damage in concrete is by general practice concluded to be a problem that can be avoided by using air-entraining agents to develop an air bubble structure in the hardened concrete together with the use of a relatively low water to cement ratio in mix. This fact is true for inner damages, however, the so-called salt-frost damage, occurring mainly at the surfaces of concrete constructions, can not totally be avoided by the above mentioned method. The performance and the mechanisms occurring in concrete, with a substantial amount of water in its micro-structure, at very low temperature are, however, in most part unknown. In this work samples of concrete at different water to cement ratios and air bubble contents subjected to freeze/thaw cycles with the lowest temperature at about -80 oC are investigated. By adopting a novel technique a scanning calorimeter is used to obtain data from which the ice contents at different freeze temperatures can be calculated. The length change caused by temperature and ice content changes during test is measured by a separate experiment using the same types of freeze-thaw cycles as in the calorimetric tests. In this way it was possible to compare the amount of formed ice at different temperatures and the corresponding measured length changes. The development of cracks in the material structure was indicated by an ultra-sonic technique by measuring on the samples before and after the freeze thaw tests. Further the air bubble structure was investigated using a microscopic technique in which air bubble size distributions and the so-called spacing factor, indicating the mean distance between air bubbles, were measured. By analyzing the experimental result it is concluded that damages occur in the temperature range of about -10 oC to 55 oC, when the air content is lower than about 4% of the total volume. For a totally water saturated (using vacuum) concrete damages always occur independently of the use of entrained air or low water to cement ratios. It is, further, concluded that the length changes of theses samples corresponds to the calculated ice contents at different temperatures in a linear fashion. Even though a quite extensive experimental investigation are performed in this work, it is concluded to be difficult to verify or reject the three most common theories for the mechanisms of inner frost damage, i.e. the closed container-, hydraulic pressure- and ice lens growth theory. The new suggested method to calculate the ice contents at different temperatures, using raw data from the adopted scanning calorimetric technique, are however ideal suited for this purpose once more directed experiments are performed.

  • 68. Johannesson, Björn
    Interaction Between Surface Change Phenomena and Multi-Species Diffusion in Cement Based Materials2008In: International Conference on Microstructure Related Durability of Cementitious Composites / [ed] W. Sun, K. van Breugel, C. Miao, G. Ye and H. Chen, Rilem publications, 2008, p. 565-574Conference paper (Other academic)
    Abstract [en]

    Measurements strongly indicate that the ‘inner’ surface of the microscopic structure of cement based materials has a fixed negative charge. This charge contributes to the formation of so-called electrical double layers. In the case of cement based materials the ionic species located in such layers are typically potassium -, sodium - and calcium ions. Due to the high specific surface area of hydrated cement, a large amount of ions can be located in theses double layers even if the surface charge is relatively low. The attraction force, caused by the fixed surface charge on ions located close to surfaces, is one possible explanation for the observed low global diffusion rates in the pore system of positively charged ions compared to the negatively charged ones. Here it is of interest to simulate the multi ionic diffusion behavior when assigning positively charged ions a comparably lower diffusion constant and also including a negatively charged ‘ion’ with an extremely low diffusion constant so as to represent a fixed negative surface charge. The theoretical results from such simulations, using a tailor made finite element technique, indicates a strong influence of surface charges on global diffusion of different ionic species in the pore system of cement based materials.

  • 69.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Ionic Diffusion and Kinetic Homogeneous Chemical Reactions in the Pore Solution of Porous Materials with Moisture Transport2009In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 36, no 4, p. 577-588Article in journal (Refereed)
    Abstract [en]

    Results from a systematic continuum mixture theory will be used to establish the governing equations for ionic diffusion and chemical reactions in the pore solution of a porous material subjected to moisture transport. The theory in use is the hybrid mixture theory (HMT), which in its general form accounts for electroquasistatics. The derived macroscopic field equations (conservation of mass, linear and angular momentum, energy and Maxwell’s equations) for the multiphase, multicomponent system are combined with the entropy inequality to obtain restrictions on constitutive equations. The so called near equilibrium results obtained from this analysis (using Lagrange multipliers to identify properties) are obtained by expanding linearly about equilibrium. The approach leads to the development of the explicit expressions for the constitutive equations. In this work the derived generalized Fick’s law of diffusion and the generalized Darcy’s law will be used together with derived constitutive equations for chemical reactions within phases. The mass balance equations for the constituents and the phases together with the constitutive equations gives the coupled set of non-linear differential equations describing the theoretical behaviour of the system under consideration. A Finite element procedure is described capable of solving the coupled set of governing differential equations. A novel approach on how to arrange the stiffness matrix of the global problem to take into account for a quite general description of chemical reactions among constituents is described. The Petrov – Galerkin approach are used in favour of the standard Galerkin weighting in order to improve the solution when the convective part of the problem is dominant. A modified type of Newton – Raphson scheme is derived for the non-linear global matrix formulation. The developed model and its numerical solution procedure are checked by running test examples which results demonstrates robustness of the proposed approach.

  • 70.
    Johannesson, Björn
    Lund Institute of Technology.
    Nonlinear transient phenomena in porous media with special regard to concrete and durability1997In: Advanced Cement Based Materials, ISSN 1065-7355, E-ISSN 1878-5948, Vol. 6, no 3-4, p. 71-75Article in journal (Refereed)
    Abstract [en]

    Concrete deteriorates due to many different mechanisms. Among the most important mechanisms is the reinforcement corrosion induced by deleterious substances reaching the embedded reinforcement bars. The external sources of deleterious materials may, for example, be deicing salts, sea water, and carbon dioxide. Research has sought to determine threshold values, in terms of concentration of deleterious substances in concrete, at which reinforcement corrosion will be induced, that is, at which concentration the passive condition close to the reinforcement turns to an aggressive state. To predict when this threshold value is reached, the flow properties of the pollutant in concrete must be known. Some of the most important phenomena governing the movement of pollutants in concrete are diffusion of substances in the pore water, adsorption (and desorption) of pollutants onto the pore walls, and hydrodynamic dispersion and convection of substances due to flow of the pore water. Here a set of equations will be presented based on mass and energy balance. These coupled equations cope with the above-mentioned phenomena. The migration of ions due to an electric potential is not considered as only the initiation stage of corrosion is of interest. The constituents considered in the model are a solute γ (e.g., chlorides), the pore water α, and the solid phase s of the concrete, which is restricted to be nondeformable. The governed equation system is solved using the Petrov-Galerkin scheme and finite elements (compare references 1 and 2). Some examples of the performance of the proposed model are given.

  • 71.
    Johannesson, Björn
    Lund Institute of Technology.
    Prestudy on diffusion and transient condensation of water vapor in cement mortar2002In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 32, no 6, p. 955-962Article in journal (Refereed)
    Abstract [en]

    The kinetics of sorption of water vapor in mature cement mortar are examined experimentally by the use of a sorption balance (DVS1000). The relative humidity in the sample chamber is obtained by mixing dry and saturated air using flow regulators with very high accuracy. A predefined change of relative humidity in the sample chamber can be obtained in about 30 s. The time needed for equilibration in terms of the mass of a finely grained mortar sample is shown to be in the order of 2500 min for a 0-96% step in relative humidity at 25 degreesC. This fact calls for a refinement of modeling of diffusion of water vapor in materials such as mortar to take into account the kinetics of sorption. The established model involves a transient mass exchange term that explicitly describes the rate of condensation at internal material surfaces. This function becomes zero when located at the equilibrium sorption isotherm. The 'global' mass diffusion velocity of water vapor in the air-filled porosity is assumed to be significantly affected by the mass concentration of liquid water in the pore space. A satisfying match between the proposed model and measurements presented by U. Daian [Transp. Porous Media 4 (1989) 1.] was obtained by using nonlinear diffusion and sorption characteristics. In order to get a satisfying match, the sorption kinetics was, however, forced to be much slower than the recorded values obtained by the sorption balance. Some speculations as to the reason of this marked difference are performed. (C) 2002 Elsevier Science Ltd. All rights reserved.

  • 72.
    Johannesson, Björn
    Lund Institute of Technology.
    Restrictions on the Rate of Absorption When Evaluating Sorption Isotherms Obtained Using a Micro-Calorimetric Technique2001In: Journal of Thermal Envelope and Building Science, ISSN 1097-1963, E-ISSN 1530-8073, Vol. 25, no 2, p. 85-100Article in journal (Refereed)
    Abstract [en]

    One interestingway of measuring sorption isotherms and heats of sorption is the newly developed micro-calorimetric method. It turns out, however, that the adsorption kinetics must be proven to be rapid enough to fulfill the assumptions behind the theory for the determination of the isotherm to be valid. Here, the lower limit of the accepted rate of adsorption will be analyzed by making calculations of the diffusion behavior in the calorimetric vessel. The evaluation of the adsorption isotherms is based on assumptions of a quasi-static nature. If the adsorption kinetics are slow the behavior in the calorimeter will turn to a more or less transient process. When the heat of adsorption is of interest and the sorption isotherm and kinetics of sorption can be determined by other methods, compensation for the transient effects can be made.

  • 73. Johannesson, Björn
    et al.
    Hosokawa, Y.
    Yamada, K.
    The effect of moiture transport and sorption hystersis on ionic multispecies diffusion in concrete2008In: International RILEM Symposium on Concrete Modelling - ConMod '08 / [ed] E. Schlangen and G. De Schutter, Rilem publications, 2008, p. 527-534Conference paper (Other academic)
    Abstract [en]

    Concrete durability is very much dependent on the moisture and ionic species concentration in the pore solution. Therefore it is of interest to find physically based models for predicting the evolution and variations of these properties for different kinds of relevant boundary conditions. A porous media technique based on the general mixture theory continuum approached is used to establish a set of governing coupled equation describing the process of interest. In this model the equations are actually derived from examine the entropy inequality of the system. Lagrange multipliers are used to identify properties such as definitions of the chemical potentials of constituents. The non-equilibrium results from such evaluations is subjected to linearization in order to obtain a generalized Darcy flow equation and a set of generalized Fickian equations including for electrical fields induced by the charge character of the mixture of ionic constituents dissolved in pore solution. The hysteresis in sorption is modelled by an explicit ‘history’ dependent assumption. The key issue in this context is to divide the moisture transport into two parts, vapour and water transport, and describing the mass exchange between them with guidance from the hysteresis equilibrium model. The coupled systems of equations are rewritten in the weak form suitable for development of finite element formulations. A Taylor expansion is performed in order to reach a Newton-Raphson iteration scheme. The tangential stiffness and tangential damping of the global system is ignorer in the equilibrium iteration obtaining a more computational economic modified Newton-Raphson scheme with good convergence properties. Numerical examples of the performance of the model are presented. The effect of hystersis in the sorption is shown to affect the diffusion of ions in the pore system. Mainly this is due to the moisture content, that is, an increased diffusion resistance at low moisture contents (and the other way around) as predicted by the hysteresis model during cases with variation of the ambient relative humidity. Further, discussions of the important influence of electrical double layers at pore walls on the global model response are performed.

  • 74.
    Johannesson, Björn
    et al.
    Technical University of Denmark, Denmark.
    Hosokawa, Yoshifumi
    Taiheiyo Cement Corporation, Japan .
    Yamada, Kazuo
    Taiheiyo Cement Corporation, Japan .
    Numerical Calculations of the Effect of Moisture Content and Moisture Flow on Ionic Multi-Species Diffusion in the Pore Solution of Porous Materials2009In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 87, no 1-2, p. 39-46Article in journal (Refereed)
    Abstract [en]

    A method to analyse and calculate concentration profiles of different types of ions in the pore solution of porous materials such as concrete subjected to external wetting and drying is described. The equations in use have a solid theoretical meaning and are derived from a porous media technique, which is a special branch of the more general mixture theory. The effect of chemical action is ignored making the presented model suitable to be implemented into codes dealing solely with chemical equilibrium. The coupled set of equations for diffusion of ionic species, the internal electrical potential and the moisture content are solved simultaneously using an implicit finite element technique, in order to avoid numerical oscillations. Important verified material behaviours are included in the model, such as the convective flow of ionic species due to moisture flow, the effect of the moisture content on the ionic diffusion resistance in the pore solution of the porous material. The Gauss’ law is included in the model in order to be able to calculate the electrical potential which develops due to small deviations from total charge neutrality among the ionic species in the pore solution. The correctness of the model should be judged from the assumptions made when developing the balance laws and the constitutive equations and the assumptions made in obtaining a working numerical calculation scheme.

  • 75.
    Johannesson, Björn
    et al.
    Technical University of Denmark, Denmark.
    Janz, Mårten
    Swedish Cement and Concrete Research Institute.
    A two-phase moisture transport model accounting for sorption hysteresis in layered porous building constructions2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 6, p. 1285-1294Article in journal (Refereed)
    Abstract [en]

    Building constructions most commonly consists of layered porous materials such as masonry on bricks. The moisture distribution and its variations due to change in surrounding environment is of special interest in such layered construction since materials adsorb different amounts of water and exhibits different transport properties. A successful model of such a case may shred light on the performance of different constructions with regards to, for example, mould growth and freeze thaw damages. For this purpose a model has been developed which is based on a two phase flow, vapor and liquid water, with account also to sorption hysteresis. The different materials in the considered layered construction are assigned different properties, i.e. vapor and liquid water diffusivities and boundary (wetting and drying) sorption curves. Further, the scanning behavior between wetting and drying boundary curves are model by introducing appropriate material constants. Special properties have to be given for the interface between different materials in the layered construction in the model to be presented. In this case it is assumed that vapor penetrates through such interfaces easily but not the liquid water phase. The model is developed by carefully examining the mass balance postulates for the two considered constituents together with appropriate and suitable constitutive assumptions. A test example is solved by using an implemented implicit finite element code which uses a modified Newton-Raphson scheme to tackle the strong non-linearities in the present problem. The numerical method is described to make it possible for the interested reader to judge the significance of the proposed technique to solve the coupled set of non-linear equations and also in order to make implementations of the proposed model easy.

  • 76.
    Johannesson, Björn
    et al.
    Lund Institute of Technology.
    Janz, Mårten
    Swedish Cement and Concrete Research Institute.
    Test of four different experimental methods to determine sorption isotherms2002In: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 14, no 6, p. 471-477Article in journal (Refereed)
    Abstract [en]

    One important property of materials is their moisture fixation capacity, i.e., their ability to hold moisture at different relative humidities. The sorption isotherm is one of the main input data in moisture diffusion models, and it can also be used to evaluate properties of the microstructure. We have used four different methods to measure the sorption isotherm of sandstone and porous glass. The first method was to equilibrate samples over saturated salt solutions. The second was a sorption balance in which small material samples were weighed as they were exposed to different relative humidities. The third method was the pressure plate extractor, in which a totally wet sample was equilibrated at various overpressures, corresponding to certain relative humidities. The fourth method was a newly developed microcalorimetric technique to measure sorption isotherms. Despite the different natures of the methods, a satisfying agreement,was found.

  • 77.
    Johannesson, Björn
    et al.
    Technical University of Denmark, Denmark.
    Nyman, U.
    Lund Institute of Technology.
    A Numerical Approach for Non-Linear Moisture Flow in Porous Materials with Account to Sorption Hysteresis2010In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 84, no 3, p. 735-754Article in journal (Refereed)
    Abstract [en]

    A numerical approach for moisture transport in porous materials like concrete is presented. The model considers mass balance equations for the vapour phase and the water phase in the material together with constitutive equations for the mass flows and for the exchange of mass between the two phases. History-dependent sorption behaviour is introduced by considering scanning curves between the bounding desorption and absorption curves. The method, therefore, makes it possible to calculate equilibrium water contents for arbitrary relative humidity variations at every material point considered. The scanning curves for different wetting and drying conditions are constructed by using third degree polynomial expressions. The three coefficients describing the scanning curves is determined for each wetting and drying case by assuming a relation between the slope of boundary sorption curve and the scanning curve at the point where the moisture response enters the scanning domain. Furthermore, assuming that the slope of the scanning curve is the same as the boundary curve at the junction point, that is, at the point where the scanning curve hits the boundary curve once leaving the scanning domain, a complete cyclic behaviour can be considered. A finite element approach is described, which is capable of solving the non-linear coupled equation system. The numerical calculation is based on a Taylor expansion of the residual of the stated problem together with the establishment of a Newton-Raphson equilibrium iteration scheme within the time steps. Examples are presented illustrating the performance and potential of the model. Two different types of measurements on moisture content profiles in concrete are used to verify the relevance of the novel proposed model for moisture transport and sorption. It is shown that a good match between experimental results and model predictions can be obtained by fitting the included material constants and parameters.

  • 78.
    Johannesson, Björn
    et al.
    Technical University of Denmark, Denmark.
    Ottosen, Lisbeth M.
    Technical University of Denmark, Denmark.
    Modeling of electromigration salt removal methods in building materials2008In: Salt Weathering on Building and Stone Sculptures, Technical University of Denmark , 2008, p. 351-360Conference paper (Other academic)
    Abstract [en]

    A model is established for the prediction of the effect of salt removal of building materials using electromigration. Salt-induced decay of building materials, such as masonry and sandstone, is a serious threat to our cultural heritage. Electromigration of salts from building materials, sensitive for salt attack of various kinds, is one potential method to preserve old building envelopes. By establishing a model for ionic multi-species diffusion, which also accounts for external applied electrical fields, it is proposed that an important complement to the experimental tests and that verification can be obtained. One important issue is to be able to optimizing the salt removing electromagration method in the field by first studying it theoretically. Another benefit is that models can give some answers concerning the effect of the inner surfaces of the material on the diffusion mechanisms and the effect of the composition of the ionic constituents on the overall behavior of the salt removal process. The model is obtained by assigning a Fick’s law type of assumption for each ionic species considered and also assuming that all ions is effected by the applied external electrical field in accordance with its ionic mobility properties. It is, further, assumed that Gauss’s law can be used to calculate the internal electrical field induced by the diffusion it self. In this manner the external electrical field applied can be modeled, simply, by assigning proper boundary conditions for the equation calculating the electrical field. A tailor made finite element code is written capable of solving the transient non-linear coupled set of differential equations numerically. A truly implicit time integration scheme is used together with a modified Newton-Raphson method to tackle the non-linearities of the present problem. Theoretical test examples are presented showing the performance of the model.

  • 79.
    Johannesson, Björn
    et al.
    Lund Institute of Technology.
    Utgenannt, Peter
    Lund Institute of Technology.
    Microstructural changes caused by carbonation of cement mortar2001In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 31, no 6, p. 925-931Article in journal (Refereed)
    Abstract [en]

    The change of specific surface area and pore size distribution due to carbonation of an ordinary Portland cement mortar is investigated. The adsorption of water vapor on noncarbonated and well-carbonated cement mortar is measured in order to evaluate the difference in specific surface area for the two samples using the BET theory. From the measured desorption the pore size distribution is calculated using the Kelvin formula. A sorption balance is used to measure the sorption characteristics for the two studied sample qualities. In this method dry and saturated air are mixed in desired proportion in a closed system. One of the benefits of the method is that the samples not are exposed to carbon dioxide during testing, i.e., undesired effects caused by carbonation on the sorption can be eliminated. The specific surface area for a noncarbonated sample was calculated, using the measured adsorption data, to be 8% higher than for the well-carbonated sample. The difference in pore size distributions was more marked than the difference in specific surface area for the two samples. The well-carbonated mortar had about twice as much volume attributed to small pores as the noncarbonated cement mortar.

  • 80.
    Johannesson, Björn
    et al.
    Taiheiyo Cement Corporation R&D Center, Japan ; Lund Institute of Technology,.
    Yamada, K.
    Taiheiyo Cement Corporation R&D Center, Japan.
    Nilsson, L-O
    Lund Institute of Technology.
    Hosokawa, Y.
    Taiheiyo Cement Corporation R&D Center, Japan.
    Multi-species Ionic Diffusion in Concrete with Account to Interaction Between Ions in the Pore Solution and the Cement Hydrates2007In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 40, no 7, p. 651-665Article in journal (Refereed)
    Abstract [en]

    The penetration and leaching of ionic species in concrete are studied by using a model based on the Nernst-Planck equations. A finite element procedure is used to solve the coupled non-linear governing equations. A numerical example is performed in which the results are compared to measured electron probe micro analysis (EPMA) data. A close agreement of the simulated results to measured data is found for the specific studied example. The model includes the ionic species Cl-, Na+, OH-, Ca2+, K+ and SO42- and solid phases with variable composition. From the EPMA measurements the total concentration profiles of Cl-, CaO, SiO2, Na2O and SO3 are evaluated on samples exposed to a 3 wt% sodium chloride solution for one year. The main task in this investigation is to quantitatively understand the underlying mechanisms and find an accurate model that gives good correlation with the experimental results concerning the multi-species action during chloride penetration. In the model the chemical interaction between ions in solids and in pore solution is assumed governed by simple ion exchange processes only. The drawback using this approach is that the chemical part is lacking important physical relevance in terms of standard solubility thermodynamics. On the other hand the presented model is capable of accurately simulate the well documented peak behavior of the chloride profiles and the measured high content of calcium ions in pore solution under conditions when also chlorides is present. In this sense the established multi-species models for concrete based on standard solubility calculations alone is still incomplete.

  • 81.
    Johansson, Anton
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Morin, Sebastian
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Utvärdering av systematiskt arbetsmiljöarbete på byggarbetsplats2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Studien innehåller en undersökning av hur NCC bedriver sitt systematiska arbetsmiljöarbete i förhållande till lagstiftningen på området. I studien har en av NCCs arbetsplatser besökts och arbetsmiljön har på den arbetsplatsen granskats i förhållande till gällande lag. Intervjuer och enkätundersökningar har utförts i samverkan med utvalda aktörer. Resultatet av studien visar att NCCs arbetsmiljöarbete i stort utförs i enlighet med Svenska lagar och föreskrifter men viss förbättringspotential har också identifierats.

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  • 82. Johansson, Erika
    et al.
    Haftor, Darek
    Linnaeus University, Faculty of Technology, Department of Informatics.
    Magnusson, Bengt
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Rosvall, Jan
    Göteborgs Universitet.
    On Building Information Modeling: an explorative study2014Report (Other academic)
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  • 83.
    Karlberg, Pontus
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Berglund, Benny
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Byte från betong- till trästomme: effekter på konstruktion och geometri2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Studien undersöker konstruktiva och geometriska skillnader mellan en betong- och träregelstomme för ett fyra vånings flerbostadshus. Byggnadens konstruktionsdelar dimensionerats med hjälp av eurokoder. I brottgränstillståndet kontrolleras knäckning, stämpeltryck och horisontallast för väggar och moment- och tvärkraft samt vippning för balkar. I bruksgränstillståndet kontrolleras nedböjning för balkarna och nedböjning samt svikt och vibrationer för bjälklaget. Byggs huset med trästomme istället för betongstomme kommer dimensionerna d.v.s. tjockleken för väggar och bjälklag att öka, vilket innebär konsekvenser för planlösningen och byggnadshöjden.

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    Byte från betong- till trästomme – effekter på konstruktion och geometri
  • 84.
    Karlsson, Anni
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Svärd, Jennie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dimensionering av lastbärande stomme för framtida påbyggnad2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Världens stadsbefolkning ökar stadigt. År 2050 förväntas världens stadsbefolkning ha ökat med 2,4 miljarder. Ytan som krävs för alla dessa människor är lika stor som Indien.

    För att kunna förtäta städer utan att de ska expandera ytmässigt krävs påbyggnation alternativt rivning av befintliga byggnader med efterföljande nybyggnation.

    I denna rapport har beräkningar gjorts på en befintlig trevåningsbyggnad för att kontrollera att utvalda särskilt viktiga element klarar en påbyggnation av två ytterligare våningar. Efter beräkningarna genomförs en jämförelse mellan den befintliga dimensionen och eventuell större dimension som kan krävas efter den tänkta påbyggnationen.

    Jämförelsen visar att en mindre förstärkning gör att de utvalda elementen klarar en påbyggnad i ett senare skede.

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  • 85.
    Karlsson, Sofie
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Geijersson, Agnes
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Optimering av en ytterväggsprodukt: En undersökning av alternativa isoleringsmaterial2018Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The AquaVilla CasaBona wall system currently contains the insulation material EPS, which has shown weaknesses while exposed to fire. The aim for this study was to suggest an alternative insulation material to EPS regarding fire, energy use and U-vale as well as energy use and carbon dioxide emissions for manufacturing. The purpose was that the suggested alternative insulation material should be able to be used by manufacturers in wall products as an alternative to EPS.

    In this study, four different insulation materials were examined by critically reviewing scientific articles and literature, as well as field studies and calculations with the energy calculation program VIP-energy. The insulation materials investigated were expanded polystyrene, polyurethane, polyisocyanurate and rockwool.

    The findings showed that EPS, PUR and PIR were not nearly as good as rockwool regarding fire. When manufacturing the various insulation materials, EPS gives the best results in terms of carbon dioxide emissions. EPS gives the best results regarding energy use for manufacturing when the insulation layer in the investigated wall system was 200 mm thick, but when the wall was given a U-value of 0,112 W/m2K, rockwool got the best results in this category. PUR and PIR gave the worst results regarding both energy use and carbon dioxide emissions at manufacturing. Rockwool generated the best results regarding energy use, but all of the materials met the requirements from Boverkets Byggregler.

    When comparing all the investigated characteristics of the various insulation materials, the most suitable material for an external wall was considered to be rockwool.

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  • 86.
    Kozłowski, Marcin
    et al.
    Silesian University of Technology, Poland.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology. Lund University, Sweden.
    Experimental investigation on timber-glass composite I-beams2014In: Challenging Glass 4- Structural Glass-Novel design methods and next generation products / [ed] Louter, Bos, Belis and Lebet, Taylor & Francis, 2014Conference paper (Refereed)
    Abstract [en]

    Timber-glass composite I-beams were manufactured and tested in bending to failure. The glass web of the I-beam was adhesively bonded to the timber flanges using three different adhesives: Epoxy, Acrylate and Silicone. For the webs two types of 8 mm thick glass were used: annealed float and heat heat-strengthened glass. Before testing the beams with heat-strengthened glass, the residual-stress profile through the thickness of the glass panels was measured using a portable scattered light polariscope SCALP. The results show that the beam stiffness was similar for the acrylate and epoxy-bonded beams, despite the difference in adhesive stiffness. The beams bonded with the silicone adhesive showed approximately 25% lower stiffness. In terms of load bearing capacity, the beams made using heat-strengthened glass were approximately 50% stronger than the beams made using annealed float, for the epoxy and acrylate adhesive. Using the silicone adhesive, the increase was approximately 20%.

  • 87.
    Larsson, Linus
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Andersson, Henrik
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Peabs arbetsberedning i produktionen: Finns det en koppling mellan arbetsberedning och Lean construction?2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Statistik har visat att byggbranschens byggnationskostnader i Sverige har ökat de senaste åren. Dessa kostnader beror enligt Josephson & Saukkorippi på kvalitetsproblem och kostnader för omprojektering, samt att det i nuläget görs aktiviteter som inte tillför något kundvärde.

     

    Ett arbetsmoment som idag är en viktig del hos många byggföretag är arbetsberedning. Syftet med arbetsberedningen är att hitta den optimala metoden att utföra ett moment på.

     

    Grunden till uppslaget är att Peab anser att det råder brister i deras nuvarande arbetsberedning. Intervjuer och enkätundersökning har gjorts för att kartlägga eventuella brister i Peabs arbetsberedning samt deras synsätt på Lean.

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  • 88.
    Latini, Chiara
    et al.
    Technical University of Denmark, Denmark.
    Zania, Varvara
    Technical University of Denmark, Denmark.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Dynamic stiffness and damping of foundations for jacket structures2015In: The proceedings of the 6th International conference on earthquake geotechnical engineering, 2015Conference paper (Refereed)
    Abstract [en]

    Foundation for offshore jacket structures may comprise of long floating piles. The dynamic response of floating piles to horizontal load is herein investigated. The analytical solution of horizontally vibrating end bearing piles by Novak & Nogami (1977) has been modified. At first the soil resistance as defined by Nogami & Novak (1977) is determined, considering 3D wave propagation within linear soil layer with hysteretic damping. Thereafter, the dynamic response of the pile is estimated assuming soil pressure equal to the soil resistance and imposing displacement compatibility. A parametric study clarifies the role of the parameters involved i.e. the depth of the soil layer, the pile diameter and the soil layer shear wave velocity. Results are presented in terms of dimensionless graphs which highlight the frequency dependency of the dynamic stiffness and damping.

  • 89.
    Lindblad, Fredrik
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Bolmsvik, Åsa
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Pettersson, Jenny
    Wiberg, Sara
    Efficiencies in the On-Site Material Handling Process by Using Radio Frequency Identification in the Wood Building Construction Industry2018In: International Journal of Innovation, Management and Technology, ISSN 2010-0248, Vol. 9, no 6, p. 252-259Article in journal (Refereed)
    Abstract [en]

    In the past decades, the housing shortage in Sweden accumulated to a level that led to problems finding accommodation for many people, which created opportunities for the market producing multi-family houses. The market is dominated by concrete solutions whereas solutions using wood as a building material only comprise 9 % of the market. This market is highly competitive with many companies offering relatively similar products or services. One way to develop new business opportunities is to enhance other competence besides production technology that currently acts as a market development barrier. Hence, the material handling process at building sites is seen as a barrier that can contribute improving competitiveness.

    There are currently problems with material handling at many building sites of wood-building solutions in Sweden, materials arrive at the wrong time, waste of storage space, unnecessary tracking of materials or wrong quantities arriving at the sites. The purpose of the study is to investigate if Radio Frequency Identification (RFID) is a technology that can be used to achieve an efficient material handling process and if the wood building industry in Sweden is willing to implement the technology. Thus, investigate if material handling using RFID can improve time effectiveness, minimise waste and monitor moisture levels in the material efficiently, creating improved competitiveness. The study shows that the use of RFID improves time efficiency and control the material handling, indicating that RFID has potential to improve this process. Further, the study identifies possibilities by using RFID technology to minimize damages and control moisture levels.

  • 90.
    Lindblad, Fredrik
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Magnusson, Bengt
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Luu, Alan
    Ragnarsson, John
    Information Flow Optimisation: Enabling Standardisation towards Modular Building Methods of Wood-Building Solutions2018In: International Journal of Innovation, Management and Technology, ISSN 2010-0248, Vol. 9, no 6, p. 232-239Article in journal (Refereed)
    Abstract [en]

    Currently, there is a considerable lack of residential buildings in Sweden. Hence, companies that are active in the housing industry producing wood-building solutions have been affected by high demand for their products. The industry tries to be more effective, and one means of achieving this goal is to automate the production, similar to the automotive industry. However, improvements in the information flow have not come as far as developments in the production. Therefore, it is necessary to streamline the entire process and reduce the amount of manual work using rationalisation and automation to enhance competitiveness. This is not only applicable to the actual manufacturing process but also in a large degree to the design process, i.e. the transition from the basic to the detail design stage. The purpose of this research is to compare the information flow for various building projects before production, identifying development possibilities by using an improved information process.

    Information has been collected into a status report using interviews, surveys and from data in the Enterprise Resource Planning (ERP) system.

    Two areas were identified out of the status report: standard projects and special projects. The special projects constitute 90 % of the project departments actual workload, whereas standard projects do not exceed the projected lead times creating less problem than special projects. Therefore, the long-term development strategy for the industry should be to improve the level of project standardisation, developing an advanced modular system based on improved information flow minimising the need for special projects.

  • 91.
    Lindblom, Mikael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Toll, Lucas
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dimensionering av infästningsplåtar i prefabricerade betongelement - viktiga parametrar2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Arbetet går ut på att för Nybro Cementgjuteri utföra dimensioneringsberäkningar för infästningsplåtar ingjutna i prefabricerade betongelement. Genom att utföra dessa beräkningar har ett beräkningsunderlag i Microsoft Excel kunnat framställas och levereras till företaget. I underlaget kan företaget föra in olika plåtparametrar som bredd, höjd och tjocklek på plåten samt förankringsstängernas längd och tjocklek med mera och få ut vilka kapaciteter plåtarna besitter gällande normalkraft, tvärkraft samt moment i tre olika riktningar.

    Dessutom har en parameterstudie utförts där det har undersökts vilka konsekvenser det skulle medföra att till exempel ändra avståndet mellan förankringsstängerna.

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  • 92.
    Lindstam, Gustaf
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Larsson, Beatrice
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Optimized utilization of raw materials for production of Cross Laminated Timber: Quality of laminations and its effects on mechanical properties of multi-layer panels2019Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Cross laminated timber (CLT) is a product increasingly demanded by the market. This has led to an interest among producers to further optimize the use of raw material. The aim of this investigation is therefore to analyze how the material properties in softwood lamellas, when used in different layers of a CLT plate, affect the stiffness and strength for CLT floor elements. This is done by analysis of CLT constructions with different dimensions, constructions and quality of lamellas. For the bending stiffness of CLT plates, the most important lamination property is the longitudinal modulus of elasticity. However, the stiffness to rolling shear of the lamellas has also large influence on the combined bending and shear stiffness of a CLT plate. The properties for the lamellas that has being used in this investigation are valid for Norway spruce (Picea Abies .L). For investigation and analysis of the lamellas and the CLT floors has Finite Element simulations by the software Abaqus (2017) along with hand calculations been used. A total of three different simulations were performed to accomplish the objectives set in this work.

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  • 93.
    Lovén, Joacim
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Kallay, Viktor
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Utredning av byggavfall och ställtider2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Studien har undersökt Botrygg ABs ställtider och uppkomsten av byggavfall. Målet har varit att optimera ställtiderna och minimera byggavfallet. Metoderna som ansågs vara lämpligast för studien var intervjuer, framtagning av statistik samt observationer. Detta genomfördes på två av Botrygg ABs byggarbetsplatser med specifikt fokus på platsen Kv. Duvkullen. Intervjupersonerna representerade inköp, logistik, plats -och byggchef. De uppnådda resultaten sett till olika moment i avfallshantering och planering mot ställtider gav möjlighet att dra slutsatser mot vad Botrygg AB kan göra för möjliga ändringar för en förbättrad produktion sett till kostnader, tidseffektivisering och ge en reducerad miljöpåverkan. Framtagna resultat är statistik av byggavfallet vid en av byggarbetsplatserna, intervjupersonernas resonemang och åsikter kring de två berörda frågor, sett till vad som kan göras bättre samt vad som i nuläget fungerar. Dessa resultat jämfördes och följande slutsatser kunde dras:

    • närmare samarbete med leverantörer,
    • vidareutveckla Just-in-time,
    • kontinuerlig kommunikation mellan berörda aktörer,
    • uppföljningar av projektens byggavfall för att se vad som genereras,
    • sätt upp ett tydligt mål om mängder byggavfall genom att t.ex. använda statistik.
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  • 94.
    Mahapatra, Krushna
    et al.
    Mid Sweden University.
    Gustavsson, Leif
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Full service energy efficient renovation business for Swedish single-family houses2011In: Proceedings of SB11 Helsinki World Sustainable Building Conference, 2011Conference paper (Refereed)
    Abstract [en]

    More than 80% of the Swedish single-family houses were built prior to 1977 when energyefficiency was introduced in the national building code. These houses are more than 30-40 yearsold and need renovation. This provides a unique opportunity for large-scale implementation ofenergy efficiency measures. However, there is a lack of business model to introduce full serviceenergy efficiency renovation packages that include consulting, contract work, follow-up andfinancing. Under the Nordic project “Successful Sustainable Renovation Business for Single-FamilyHouses – SuccessFamilies”, we have conceptualized a new business model to offer such a fullservice package to the Swedish homeowners. The new business could be offered by existingconstruction/renovation companies in collaboration with energy auditors/building consultants andheating system retailers/installers. The business could be targeted to houses built during 1971-80as the primary energy efficiency potential is significant in this segment. Especially houses that areon sale could be targeted because people usually do indoor renovation when they buy a houseand therefore, they may be interested in energy efficient renovations. Banks may consider postrenovation value of the newly-bought house based on planned renovation package from anentrepreneur to provide increased mortgage finance for renovation. Other options to improveenergy efficient renovation of single family houses include tax subsidies, preferential loans andguarantee on energy or energy cost savings.

  • 95.
    Mahapatra, Krushna
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Gustavsson, Leif
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Haavik, Trond
    Segel As, Norway.
    Aabrekk, Synnøve
    Segel As, Norway.
    Svendsen, Svend
    Danish Technical University, Lyngby, Denmark.
    Tommerup, Henrik
    Technical University of Denmark.
    Ala-Juusela, Mia
    VTT, Espoo, Finland.
    Paiho, Satu
    VTT, Espoo, Finland.
    Report on possible financing schemes for one-stop-shop service for sustainable renovation of single family house, Deliverable D3.1 of the project Successful Sustainable Renovation Business for Single-Family Houses – SuccessFamilies2011Report (Other academic)
  • 96.
    Mahapatra, Krushna
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Gustavsson, Leif
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Haavik, Trond
    Segel As, Norway.
    Aabrekk, Synnøve
    Segel As, Norway.
    Svendsen, Svend
    Danish Technical University, Lyngby, Denmark.
    Vanhoutteghem, Lies
    Technical University of Denmark.
    Paiho, Satu
    VTT, Espoo, Finland.
    Ala-Juusela, Mia
    VTT, Espoo, Finland.
    Business models for full service energy efficient renovation of single family houses in Nordic countries2012In: ICAE2012, 2012, p. 593-602Conference paper (Refereed)
    Abstract [en]

    In Nordic countries significant primary energy efficiency potential exists in houses built before 1980. These old houses need to be renovated, which provides an opportunity for implementation of energy efficiency measures. However, there are several economic and market barriers and the renovation market are dominated by handicraft-based individual solutions. In this project we analyze the opportunities for implementation of one-stop-shop business models where an overall contractor offers full-service renovation packages including consulting, independent energy audit, renovation work, follow-up (independent quality control and commissioning) and financing.

    A comparative assessment of emerging business models shows that different types of actors (renovation company, insulation company, energy utility, building product warehouse) can provide such a service. Financing is included in some models. There are differences in how customers are contacted, while the similarities are more on how the service is provided. A main challenge is how to secure independent advising and there is there is uncertainty over who will be responsible for guarantee of the renovation work if the service provider goes bankrupt.

    Even though there is strong business potential for one-stop-shop energy renovation concept, still it has been somewhat difficult to start or run such a business. Various options to overcome the barriers to promote energy efficient renovation of detached houses are discussed.

  • 97.
    Mahapatra, Krushna
    et al.
    Mid Sweden University, Sweden.
    Gustavsson, Leif
    Mid Sweden University, Sweden.
    Haavik, Trond
    Segel AS, Norway.
    Aabrekk, Synnøve
    Segel AS, Norway.
    Tommerup, Henrik
    Technical University of Denmark, Denmark.
    Svendsen, Svend
    Technical University of Denmark, Denmark.
    Paiho, Satu
    VTT, Finland.
    Ala-Juusela, Mia
    VTT, Finland.
    Report on business models for one-stop-shop service for sustainable renovation of single family house, Deliverable D3.2: Successful Sustainable Renovation Business for Single-Family Houses – SuccessFamilies2011Report (Other academic)
    Abstract [en]

    In Nordic countries significant primary energy efficiency potential exists in houses built before 1980. These houses are more than 30 years old and need to be renovated. This provides an opportunity for implementation of energy efficiency measures, but the renovation market is dominated by handicraft-based individual solutions. There is a need for one-stop-shop business models where an overall contractor offers full-service renovation packages including consulting, independent energy audit, renovation work, follow-up (independent quality control and commissioning) and financing. There is a significant business potential for such a model as the renovation market for single-family houses could be in the order of hundreds of million Euros per year in each Nordic country. Homeowners will get an improved quality renovated house with little risk or responsibility which usually is the case with traditional renovations, the energy cost will be reduced, market value of the house is likely to increase, mortgage banks will have a safer asset and there are societal benefits in terms of reduced energy use and greenhouse gas emission. However, there is uncertainty over who will be responsible for guarantee of the renovation work if the service provider goes bankrupt. Insurance companies could be involved to address this issue.

    The aim of the report is to analyze and develop one-stop-shop business models to offer full-service renovation packages in the Nordic countries. The report will contribute to identify potential models that can be tested in pilot studies and will be an important source of market information for companies planning to develop a one-stop-shop concept.

    A comparative assessment of models proposed in the Nordic countries shows that different type of actors may play the key role in a one-stop-shop for energy efficient renovation of single-family houses. In some models the service provider collaborates with financing institutions to provide renovation financing. There are differences on how customers are contacted, while the similarities are more on how the service is provided. A main challenge is how to secure independent advising.

    Even though there is strong business potential for one-stop-shop energy renovation concept, still it has been somewhat difficult to start or run such a business. One of the main reasons is the uncertainties about the customer base. One way to attract more customers is to offer subsidies for energy efficiency measures. In Denmark, Sweden and Finland there are tax deductions for labour cost for home renovation and other household work. An amendment to such programs to incorporate specific requirements regarding energy efficiency of implemented measures could be a way to increase homeowners’ interest in energy efficient renovation.

    A guarantee on energy or energy cost saving may encourage energy efficient renovation of houses as energy cost saving is one of the most important factors in the homeowners’ decision to implement energy efficiency measures. But, at present it is less likely that such guarantee will be given as the full service energy renovation concept is yet to be tested and not enough experience exists regarding energy savings potential in the context of varying household energy behaviour. However, such concepts exist for industrial and public buildings (the ESCO concept) and are emerging for residential buildings. Highlighting the energy (e.g. cost reduction) and non-energy benefits (improved thermal comfort or indoor air quality) of energy efficiency improvements may create customer interest in energy efficient renovations.

    One way to kickstart the market is to provide public funding for few demonstration projects to test different business models, e.g. those identified in this report. Such projects will bring together actors interested in one-stop-shop concept and they will gain some experience. In such demonstration projects the full-scale energy renovation actions could be realised in shorter timeframe than in traditional piecemeal renovations. Advertisement of results of successful demonstration projects may attract more customers and entrepreneurs.

    Existing models in Denmark and Finland include financing by the service providers in collaboration with financing institutions. Still, mortgage financing is the most cost efficient option to finance energy efficiency renovation of single-family houses (Mahapatra et al. 2011). However, the need to selffinance the amount not covered in the mortgage loan may not encourage homeowners to go for energy efficiency renovation. This could be addressed if government provides soft loans or subsidies to cover the investment cost beyond the mortgage (base) loan. Attention should be given to the limitation of mortgage financing for energy efficient renovation of recently bought houses. Banks may consider an energy efficient renovation plan prepared by an entrepreneur and pre-evaluate the postrenovation value of the house in collaboration with real estate agents. This valuation could form the basis for the bank to confirm the homeowner and the entrepreneur that certain amount of investment cost would be covered by mortgage refinancing.

  • 98.
    Mahapatra, Krushna
    et al.
    Mid Sweden University.
    Gustavsson, Leif
    Mid Sweden University.
    Haavik, Trond
    Segel As, Norway.
    Aabrekk, Synnøve
    Segel As, Norway.
    Vanhoutteghem, Lies
    VTT, Finland.
    Svendsen, Svend
    Danish Technical University, Lyngby, Denmark.
    Paiho, Satu
    VTT, Espoo, Finland.
    Ala-Juusela, Mia
    VTT, Espoo, Finland.
    One-stop-shop service for sustainable renovation of single family house: Summary Report2012Report (Other academic)
    Abstract [en]

    The Nordic project “Successful Sustainable Renovation Business for Single-Family Houses (SuccessFamilies)”, with participants from Denmark, Finland, Norway and Sweden, deals with development of business models for full service energy efficient renovation of detached houses in Nordic countries. The background to this project is that the majority of these houses are more than 30 years old and need to be renovated, which provides opportunity for implementation of energy efficiency measures. The renovation market is dominated by handicraft-based individual solutions. There is a need for onestop-shop business models where an overall contractor offers full-service renovation packages including consulting, independent energy audit, renovation work, independent quality control and commissioning, and financing. There is a significant business potential for such a model as the volume of renovation market for single-family houses can reach hundreds of million Euros per year in each Nordic country. The project team analysed emerging business models to offer full-service renovation packages in the Nordic countries. A comparative assessment shows that different types of actors (renovation company, insulation company, energy utility, building product warehouse) can provide such a service. There are differences in how customers are contacted, while the similarities are more on how the service is provided. A main challenge is how to secure independent advising. Even though there is strong business potential for one-stop-shop energy renovation concept, still it has been somewhat difficult to start or run such a business. Various options to overcome the barriers to promote energy efficient renovation of detached houses are discussed in the final report.

  • 99.
    Mainali, Brijesh
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Mahapatra, Krushna
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Pardalis, Georgios
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Evaluating Existing Market for Deep Energy Renovation in Sweden and Denmark2018In: Advanced Building Skins: C2 Models, Policies and Products for Building Retrofit, Wilen (Sarnen): Advanced Building Skins. ABS, 2018, p. 576-580Conference paper (Other academic)
    Abstract [en]

    Buildings are responsible for 40% of energy consumption and 36% of CO2 emissions in the EU. Sweden andDenmark are cold climatic countries with strong demand for space heating and hot water in the residentialsector. Large section of the detached houses in these countries are built more than 30 years ago and needrefurbishment. Despite of huge energy saving potentials with deep renovation of these houses, there existsseveral challenges in realizing those saving potentials. This paper evaluates the market for deep renovation ofsingle-family houses in these two Nordic countries using PEST and SWOT analysis. Comparative analysisbetween two countries will help to understand the common and country specific drivers and barriers and todevelop strategic recommendation in accordance.

  • 100.
    Muszyński, Lech
    et al.
    Oregon State University, USA.
    Akter, Shaheda T.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Nairn, John
    Oregon State University, USA.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    On the need for reliable rolling shear characteristics in CLT lamellas and for efficient related test methods2019In: Bool of abstract: CompWood 2019, International Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber Structures. June 17-19, 2019, Växjö, Sweden., Lnu Press , 2019Conference paper (Refereed)
    Abstract [en]

    Effective modeling of structural behavior of cross-laminated timber (CLT) elements requires reliable input on the mechanical properties of its laminations. The cross-lamination of layers provides for dimensional stability of CLT elements. In this arrangement, however, all laminations in shear walls and the layers of floor elements oriented perpendicular to the major strength axis transfer shear stress in the radial–tangential plane, often referred to as rolling shear. It is among the least documented characteristics of wood, since it had been of marginal interest for structural lumber and engineered wood composites until the emergence of CLT. While the numerical models may easily account for the contribution of rolling shear in the immediate and long-term deformations of laminated panels, simulations are charged with wide margins of uncertainty because of shortage of reliable experimental data. Rolling shear is not the easiest property to measure, and it received only limited coverage in the literature [1-7]. What has been documented was that the rolling shear strength and stiffness in the cross-layers in CLT floor panels is related to the species, density, growth ring orientation, and manufacturing parameters, but there is no evidence for a meaningful correlation with the grade of lumber, whether established by visual or machine grading. In the presentation, we will discuss the pressing need for reliable data on rolling shear characteristics in clear wood and in structural lumber, their statistical distributions in species important for CLT industry, as well as for efficient test methods to allow generation of relevant data in timely manner. Prototype methods and preliminary data will be presented.

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