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  • 151.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology.
    Jacquier, Nicolas
    Byggnadstekniska Byrån.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Stiffness model for inclined screws in shear-tension mode in timber-to-timber joints2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 136, p. 580-595Article in journal (Refereed)
    Abstract [en]

    A stiffness model for inclined screws in timber joints, or as shear connectors in composite timber-to timber members, is presented. Elastic conditions applicable to the initial or linearized part of the load deformation response in the serviceability limit state are assumed. The model for the stiffness or slip modulus is general in nature; it includes both the dowel (or shearing) action and withdrawal action of the screw, the friction between the members and it takes into account possible dissimilar properties and geometries of the different parts of the joint configuration. The model is simplified in the sense that the screw is assumed rigid and the withdrawal stresses along the length of the screw are assumed evenly distributed. However, the effects of flexibility and extensibility of the screw are taken into account by applying a theoretically derived correction factor for the embedment and withdrawal stiffness modulus, respectively. The proposed model is illustrated showing the total stiffness versus the inclination, as well as the relative contributing effect from the shearing and withdrawal stiffness, respectively, the influence of the friction coefficient. Also, the effect of dissimilar properties and geometries between the two parts of the joint is illustrated. Experimental verification of the proposed model is also given. Comparisons with other stiffness models are also made. (C) 2017 Elsevier Ltd. All rights reserved.

  • 152.
    Girhammar, Ulf Arne
    et al.
    Luleå Univ Technol.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Design against brittle failure of bottom rails in shear walls2016In: Proceedings of the Institution of Civil Engineers: Structures and buildings, ISSN 0965-0911, E-ISSN 1751-7702, Vol. 169, no 10, p. 782-793Article in journal (Refereed)
    Abstract [en]

    The authors have developed a new plastic design method for light-framed timber shear walls, which is capable of analysing the load-bearing capacity of partially anchored shear walls. For proper application of the plastic method it is necessary to ensure ductile behaviour of the sheathing-to-framing joints and to avoid brittle failure of the bottom rail. In a partially anchored shear wall, the tying down forces are developed in the sheathing-to-framing joints along the bottom rail, which may introduce a brittle type of failure of the bottom rail that needs to be eliminated in order for the plastic method to be applicable. This paper deals with design of anchor bolts needed to tie down the bottom rail properly and it describes experimental results for proper design of washers for anchor bolts to avoid these splitting failures of the bottom rail. The effect of different washer sizes and location of the anchor bolts on the failure load when splitting of the bottom rail occurs is presented. The tests indicate that the failure load depends on the distance from the edge of the washer to the loaded edge of the bottom rail. An explicit design equation for the capacity of the bottom rail is presented.

  • 153.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Horizontal Stabilisation of Sheathed Timber Frame Structures Using Plastic Design Methods - Introducing a Handbook Part 1: Design Principles for Horizontal Stabilisation2016In: WORLD MULTIDISCIPLINARY CIVIL ENGINEERING-ARCHITECTURE-URBAN PLANNING SYMPOSIUM 2016, WMCAUS 2016, Elsevier, 2016, p. 618-627Conference paper (Refereed)
    Abstract [en]

    The authors have developed a plastic design method for sheathed timber frame shear walls. It has been presented and discussed for inclusion in Eurocode 5 and a Swedish handbook has been presented. In the plastic method, you can choose to transfer the anchoring force via the leading stud to the substrate, corresponding to a fully anchored shear wall (no uplift of studs), but you can also choose to utilize the sheathings to transfer the tensile force via the sheathing-to-framing joints to the substrate by anchoring the bottom rail, corresponding to a partially anchored shear wall (studs experience uplift). By the plastic method several alternatives for anchoring the wall are possible and they can also be combined in such a way that each of them take a portion of the uplifting force, e.g. through a simple tying down device, through the sheathing-to-framing joints and through anchoring of the shear wall to the transverse wall. The method also makes it possible to include the load-bearing capacity of wall segments including openings. The handbook treats primarily shear walls, but for the sake of completeness some aspects of the roof and floor diaphragms are also discussed. The interior force distribution in sheathed timber frame walls weak in shear is discussed, as are the fundamental difference between the effect of vertical loads on the stabilisation of walls which are rigid or weak in shear, and how the plastic design method is applied to multi-storey timber buildings. (C) 2016 The Authors. Published by Elsevier Ltd.

  • 154.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Horizontal Stabilisation of Sheathed Timber Frame Structures Using Plastic Design Methods - Introducing a Handbook Part 2: Design of Joints and Anchoring Devices2016In: WORLD MULTIDISCIPLINARY CIVIL ENGINEERING-ARCHITECTURE-URBAN PLANNING SYMPOSIUM 2016, WMCAUS 2016, Elsevier, 2016, p. 628-635Conference paper (Refereed)
    Abstract [en]

    In this part 2, the practical design and strength of a number of different joints is described: (1) Sheathing-to-framing joints the plastic design method is based on the premise that the load-displacement relationship of the sheathing-to-framing joints has sufficiently large plastic deformation capacity; the sheathing-to-framing joints have great influence on the load-carrying capacity of the wall; (2) Stud-to-rail joints by utilizing the shear capacity of the stud-to-rail joints, the plastic design method can be simplified and the load-carrying capacity can be increased; (3) Hold down devices for the (leading) stud - the capacity of the tying down force of the hold down determines whether the shear wall will act as fully or partially anchored; tying down the shear walls by connecting them to the transverse walls leads to a 3-dimensioonal behaviour that is a very favourable for the load-carrying capacity and the stiffness of the shear wall; through transverse walls the anchoring of the leading stud can be reduced or eliminated (those types of transverse wall connections are not discussed in detail in this paper); and (4) Anchoring devices for the bottom rail in - partially anchored shear walls it is necessary that the bottom rail is anchored to the substrate against uplift. Characteristic values for the different types of joints are given. Also, joints between the panels in the walls, roofs and floors are described briefly. (C) 2016 The Authors. Published by Elsevier Ltd.

  • 155.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Tests and Analyses of Slotted-In Steel-Plate Connections in Composite Timber Shear Wall Panels2017In: Advances in Civil Engineering / Hindawi, ISSN 1687-8086, E-ISSN 1687-8094, article id 7259014Article in journal (Refereed)
    Abstract [en]

    Theauthors present an experimental and analytical study of slotted-in connections for joining walls in the Masonite flexible building (MFB) system. These connections are used for splicing wall elements and for tying down uplifting forces and resisting horizontal shear forces in stabilizing walls. The connection plates are inserted in a perimeter slot in the PlyBoard (TM) panel (a composite laminated wood panel) and fixed mechanically with screw fasteners. The load-bearing capacity of the slotted-in connection is determined experimentally and derived analytically for different failure modes. The test results show ductile postpeak load-slip characteristics, indicating that a plastic design method can be applied to calculate the horizontal load-bearing capacity of this type of shear walls.

  • 156. Godinho, Pedro Miguel Jesus de Sousa
    et al.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Eberhardsteiner, Josef
    Hellmich, Christian
    Multiscale modelling of transversely isotropic and anisotropic planar fiber networks: current results for elasticity and strength of paper, and potential applications to related materials2018In: Engineering Mechanics Institute Conference 2018 (EMI 2018), Cambridge, Massachusetts, USA, 2018Conference paper (Refereed)
  • 157.
    Godinho, Pedro Miguel J.S.
    et al.
    Vienna University of Technology (TU Wien), Austria.
    Jajcinovic, Marina
    Graz University of Technology (TU Graz), Austria.
    Wagner, Leopold
    Vienna University of Technology (TU Wien), Austria.
    Vass, Viktoria
    Vienna University of Technology (TU Wien), Austria.
    Fischer, Wolfgang
    Graz University of Technology (TU Graz), Austria.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Hirn, Ulrich
    Graz University of Technology (TU Graz), Austria.
    Bauer, Wolfgang
    Graz University of Technology (TU Graz), Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology (TU Wien), Austria.
    Hellmich, Christian
    Vienna University of Technology (TU Wien), Austria.
    A continuum micromechanics approach to the elasticity and strength of planar fiber networks: Theory and application to paper sheets2019In: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 75, p. 516-531Article in journal (Refereed)
    Abstract [en]

    2D materials such as planar fibrous networks exhibit several mechanical peculiarities, which we here decipher through a 3D-to-2D transition in the framework of continuum micromechanics or random mean-field homogenization theory. Network-to-fiber concentration (or “downscaling”) tensors are derived from Eshelby-Laws matrix-inclusion problems, specified for infinitely long, infinitely flat fibers, and for infinitely flat spheroidal pores of vanishing stiffness. Overall material failure is associated with microscopic shear failure orthogonal to the fiber direction. Corresponding structure-property relations between porosity on the one hand, and in-plane stiffness as well as strength on the other hand, appear as linear. This is in good agreement with mechanical experiments carried out on pulp fibers, on pulp fiber-to-pulp fiber bonds, and on corresponding paper sheets.

  • 158.
    Godinho, Pedro M.J.S.
    et al.
    Vienna University of Technology, Austria.
    Jajcinovic, Marina
    Graz University of Technology, Austria.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Fischer, Wolfgang. J.
    Graz University of Technology, Austria.
    Bauer, Wolfgang
    Graz University of Technology, Austria.
    Hellmich, Christian
    Vienna University of Technology.
    A continuum micromechanics approach to the strength of planar fiber networks: paper material applications2017In: CompWood 2017 - Computational Methods in Wood Mechanics - From Material Properties to Timber Structures: Programme & Book  of Abstract / [ed] Josef Füssl, Thomas K. Bader, Josef Eberhardsteiner, Vienna: TU verlag , 2017Conference paper (Refereed)
  • 159. Godinho, Pedro M.S.J.
    et al.
    Jajcinovic, Marina
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Fischer, Wolfgang J.
    Hirn, Ulrich
    Bauer, Wolfgang
    Hellmich, Christian
    A continuum micromechanics approach to the strength of planar fiber networks: paper material applications2017In: Vienna Young Scientists Symposium, June 1-2, 2017, Vienna, Austria, 2017Conference paper (Refereed)
  • 160.
    Gottfridsson, Simon
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Eriksson, David
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Riskreduceringsmetod för entreprenörer vid anbudslämnande2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Examenarbetet handlar om hur entreprenörer med hjälp av en checklista ska kunna identifiera, analysera och minimera risker som uppstår när ett förfrågningsunderlag börjar studeras till att ett eventuellt anbud lämnas. Syftet med examensarbetet är att entreprenörerna ska känna sig säkra när de lämnar anbud på ett förfrågningsunderlag. För att uppnå målet har tre stycken intervjuer genomförts och fem förfrågningsunderlag samt litteratur studerats. Resultatet av examensarbetet presenteras i form av en checklista som entreprenörerna kan använda sig av för att medvetandegöra risker vid anbudslämning och att entreprenören ska kunna använda den för att öka chansen att vinna anbudet.

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    Riskreduceringsmetod för entreprenörer vid anbudslämnande
  • 161.
    Gren Bernhäll, Oscar
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Nilsson, Adam
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bestämning av mekaniskaegenskaper för ett bio-kompositmaterial2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of the work is the determination of flexural properties for thebiocomposite Durapulp. The study includes laborative tests on Durapulp andreference materials, commonly used in the building sector. Stiffness and strength of Durapulp show that it has the potential as a replacement for conventional wood-based materials.

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  • 162.
    Grennborg, Frida
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Larsson, Sofia
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Granskning av tidplaner: hur kan arbetet bli effektivare?2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Tidsplanering är en viktig del i styrningen av byggprojekt. Olika typer av tidplaner kan användas i projekt, beroende på storlek och vilken fas det befinner sig i. Studien granskar tidplanerna från tre tidigare flerbostadshusprojekt som Skanska har byggt. Utifrån detta analyseras och jämförs planerna med hur projekten lyckats med avseende på tidshållning. Syftet med studien är att ge Skanska möjlighet att utveckla tidplaneringsarbetet.

    Studien avslutas med rekommendationer kring viktiga byggstenar i tidplanerna och vilka planer som är viktiga att använda. Analysen omfattar även användandet av programmet ”Asta Powerproject” som används för upprättande av tidplanerna. 

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  • 163.
    Gröndahl, Alexander
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Wernersson, Gustav
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Projektering av markarbete, parkeringsplatser, cykelställ m.m2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Arbetet tar upp lösningsförslag och val av lösning för en unik parkeringsplats på ett företag i Emmaboda. Lösningarna omfattar lokalt omhändertagande av dagvatten, val av beläggningstyper och trafiksäkerhet. Arbetet kommer att användas av Xylem till förfrågningsunderlaget för kommande anläggning av parkeringen.

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  • 164.
    Gustafsson, Ludwig
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Robin
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vertikalförskjutningar i ett flerbostadshus med lastbärande trästomme2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Wood is a recyclable building material and a natural supply. Building in wood is environmentally friendly and is becoming increasingly demanding. But building high structures in wood has its difficulties. That wood becomes deformed by both loadstrain and moisture variation is one of these difficulties. This report is a basis for the experiments that Linnaeus University is going to perform to study these deformations, so called vertical displacements. At Torparängen in Växjö, Derome will build a number of multi-story residential buildings of modules with load-bearing wooden frames. At the highest of these houses, data for temperature, relative humidity, moisture content and vertical displacements in and around the house's body will be collected using sensors. The sensors will be placed in the construction during the erection of the building. Based on previous experiments in the field, preparations for placement of the sensors have been made and motivated. A theoretical calculation of vertical displacement was also made. This in order to later compare the theory with reality. The main conclusion of the work was to minimize the proportion of wood loaded perpendicular to the fibers. Because it is the weakest part in the construction for vertical displacements. Furthermore, it was concluded that moisture content variation in the wood is the main reason for the total vertical deformations.

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    Examensarbete
  • 165.
    Habite, Tadios
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Florisson, Sara
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vessby, Johan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Numerical Simulation of Moisture-Induced Crack Propagation in Dowelled Timber Connection Using XFEM2018In: 2018 World Conference on Timber Engineering (WCTE), August 20-23, 2018, Seoul, Republic of Korea, World Conference on Timber Engineering (WCTE) , 2018Conference paper (Refereed)
    Abstract [en]

    At times dowelled glulam timber connections experience crack development in the fibre direction. The main reason for this is moisture variation in the timber elements which induces a stress perpendicular to the fibre direction. The aim of this paper is to study the influence of different moisture conditions and vertical dowel spacing on crack development through numerical simulations by use of the finite element method in three dimensions. A transient non-linear Fickian moisture diffusion model is implemented to simulate the moisture state within the glulam beam. The moisture gradient in the diffusion model was created by adopting a physical scenario by assuming what conditions the considered glulam beam will go through, from the factory up to installation. Further, an extended finite element method (XFEM) for two different vertical dowel spacing, 100 mm and 300 mm, with a linear elastic fracture mechanics (LEFM) approach was applied for the crack simulation. The results reveal that the moisture variation in combination with unfavourable placement of dowels can cause a crack to develop in the glulam timber beam. Moreover, it was shown that a moisture induced crack development may be modelled successfully by use of an Extended Finite Element Method (XFEM) approach.

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  • 166.
    Habite, Tadios
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Automatic detection of pith location along boards of Norway spruce on the basis of data from optical scanning of longitudinal surfaces2019In: CompWood 2019 - International Conference on Computational Methods in Wood Mechanics - from material properties to Timber Structures, Växjö, Sweden, June 17-19, 2019, Växjö: Lnu Press , 2019, p. 64-64Conference paper (Refereed)
    Abstract [en]

    Different mechanical and physical properties of wood are related to the location of pith. Norway spruce wood from the centre of logs, close to the pith, is characterized by lower longitudinal MOE, larger spiral grain angle, and larger longitudinal shrinkage coefficient than what wood farther away from the pith is [1]. Thus, knowledge of pith location along timber boards may play an important role in both appearance grading and in assessment of mechanical properties such as strength [2]. The current work aims to develop an algorithm which is capable of automatically estimating the pith location of Norway spruce boards, along the boards’ length direction, by utilizing optical scanning of longitudinal surfaces. The initial step of the algorithm is to identify defect free sections along the timber board. This is done by utilizing data from tracheid effect scanning of the four sides of the timber board. Thereafter, a continuous wavelet transform (CWT), similar to fast Fourier transform, is applied on grey scale images from scanning, to analyse the variation of light intensity across the four surfaces at selected positions along the board. Obtained local frequencies correspond to the local annular ring pattern on surfaces. Then, assuming that annular growth rings are concentric circles with the pith in the centre, detected local annular ring wavelengths (using CWT) and artificial annual ring wavelengths corresponding to different hypothetical locations of pith are compared, and an optimization procedure is used to identify the location of pith that minimizes the discrepancy between the detected and artificial sets of annular ring wavelengths. Figure 1 shows grey scale images of short segments of longitudinal surfaces, graphs of the detected local annual ring widths, and a photograph of the board cross section where the determined location of pith is marked out. Preliminary results reveal that data from optical scanners and the suggested method allow for accurate detection of annular ring width and location of pith along boards.

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  • 167.
    Habite, Tadios
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Detection of Pith Location of Norway Spruce Timber Boards on the Basis of Optical Scanning2019In: Proceedings, 21st international nondestructive testing and evaluation of wood symposium: Freiburg, Germany / [ed] Xiping Wang; Udo H. Sauter; Robert J. Ross, Madison, U.S.A: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory , 2019, p. 268-275Conference paper (Refereed)
    Abstract [en]

    Optical scanners are used in the woodworking industry to detect various defects, such as dead and live knots, cracks, and fibre distortions, which are important for the visual appearance grading of wood. Data from scanning is also used to assess mechanical properties such as bending and tensile strength, for the purpose of machine strength grading of sawn timbers. Knowledge of annular ring width and location of pith in relation to board cross-sections, and how these properties vary in the longitudinal direction of boards, is relevant for many purposes, such as assessment of shape stability and mechanical properties of timber. Therefore, the purpose of the present research is to evaluate possibilities to determine annular ring width and location of pith on the basis of scanning of surfaces parallel to the longitudinal board direction. The first step of this novel method is to identify clear wood sections, free of defects along boards. Then time-frequency analysis is applied to assess the variation of light intensity over surfaces of these sections, such that local wavelengths, related to the annular ring width patterns are detected on all four surfaces around the board. Finally, the location of pith is calculated by comparing annular ring width distributions on the different surfaces, and assuming that annular rings are concentric circles with the pith in the centre. Results indicate that optical scanners and the suggested method allow for accurate detection of annular ring width and location of pith along boards.

  • 168.
    Habite, Tadios Sisay
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Moisture-induced crack development in timber beams: a parametric study performed on dowelled timber connections2017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A problem has been observed by many researchers regarding the cracks caused mainly by moisture variation in timber structures. However, this effect has been neglected over the past decades. In addition, many design codes do not have a room for a realistic formulation of the moisture diffusion and its effect in causing internal stress, deformation, and cracks. Moreover, if this effect occurs in connection areas, usually the weakest structural section, it has and also had shown a devastating effect on the service life of many wooden structures. In the current work, a Fickian moisture diffusion model is implemented by use of finite element simulation with the help of the commercial software ABAQUS for a dowelled beam column connection. The results of such moisture diffusion were used to analyse the stress situation inside the timber section. Moreover, an extended finite element method was applied in ABAQUS to investigate how moisture induced crack develops into the timber section. Furthermore, a parametric study was performed by using Python scripting to investigate the effect of dowel spacing (horizontal and vertical) and critical energy release rate on the development of the moisture-induced crack. The results obtained revealed that for the same material property when the dowel spacing increases (either horizontal or vertical) the crack length increases significantly. Likewise, the crack length increases when the critical energy release rate requirement of the timber is decreasing.

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    Tadios_Habite_MSc_thesis
  • 169.
    Hallingbäck, Henrik R.
    et al.
    Swedish University of Agricultural Sciences.
    Högberg, Karl-Anders
    The Forestry Research Institute of Sweden.
    Säll, Harald
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Lindeberg, Johan
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Jansson, Gunnar
    The Forestry Research Institute of Sweden.
    Optimal timing of early genetic selection for sawn timber traits in Picea abies2018In: European Journal of Forest Research, ISSN 1612-4669, E-ISSN 1612-4677, Vol. 137, no 4, p. 553-564Article in journal (Refereed)
    Abstract [en]

    In breeding Norway spruce, selection for improved growth and survival is performed at age 10-15 years in order to optimize genetic gain per year. We investigated whether a selection based on wood traits such as density and grain angle, measured under bark in the field at the same age would be informative enough with respect to structural quality traits of sawn boards. To achieve this objective, a sawing study was conducted on the butt logs of 401 trees from a 34-year-old Norway spruce progeny trial situated in southern Sweden. Stem discs were excised from the top of the logs and radial profile data of grain angle, and wood density was recorded for specific annual rings. The sawn and dried boards were assessed for structural traits such as twist, board density, bending stiffness (static modulus of elasticity, sMoE) and bending strength (modulus of rupture, MoR). Additive genetic correlations (r (a)) between single annual ring density measurements and board density, sMoE and MoR were consistently strong (r (a)> 0.7) for annual rings 5-13. Genetic correlations of similar magnitude between grain angle and board twist were estimated for all investigated annual rings (from 2 to around 26 under bark). Consequently, it was found that indirect selection for wood density and grain angle at the tree age 10-16 years would result in more genetic gain per year than selection at later ages. This makes it feasible to perform simultaneous selection of progeny in the field for both growth and wood traits at similar ages.

  • 170.
    Hansen, Fredrik
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Palmquist, Jesper
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Från CAD till BIM inom småhusindustrin2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    BIM står för Building Information Modeling. Det är en ny teknik för att konstruera en virtuell modell av en byggnad i digitalt format. De stora fördelarna med BIM är att alla komponenter som läggs till i modellen innehåller information. Av informationen genereras automatiskt de handlingar och listor som behövs. Dessutom fås presentationsmaterial i form av 3D-modeller utan något extra arbete. Undersökningen behandlar ett företag och varför de inte genomfört en övergång från 2D-CAD till BIM och syftet är därför att visa dem vilka effektiviseringsmöjligheter som finns. 

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  • 171.
    Harrysson, Jacob
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Strandman, Johanna
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Ökad återvinning med en ny design av miljöhus2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This work shows a design proposal of a modern recycling house, which is developed to ease waste sorting in a community, based on architectural och technical functions. The work is based on the constantly growing environmental issues that affects planet earth. Waste sorting och recycling are two important factors that have to be further developed to contribute to a reduced climate change.

    The study is based on previous produced theories, observations, surveys and interviews with experts in different areas. The results shows that a recycling house with no front or back and without entrance, makes it easier for people to engage in waste sorting.

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  • 172.
    Hellgren, Rebecca
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Holmström, Rana
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Karin
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Direktljud genom olika friskluftsventiler och dess påverkan på boendekvalitén2017Independent thesis Basic level (professional degree), 180 HE creditsStudent thesis
    Abstract [en]

    A survey is conducted to link sound reduction index with human experiences, the survey shows that the majority of residents value silence in their homes. About one in five residents hear that sound enters their home via the fresh air vents and is willing to pay for a soundproof fresh air vents. The results of the calculations indicate that the reduction index for the measurement object is 29 dB which means that the reduction rate will be 36.6 dB after installation of soundproofed fresh air vent. When switching to a soundproof air vent, an increase of 7,6 dB in sound reduction index is achieved. By providing more information to customers about different air vents with regard to acoustics, knowledge of the subject increases and they can actively take a stand to improve their quality of accommodation. 

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  • 173.
    Hermansson, Denise
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Nilsson, Olivia
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Capacity and lifetime analysis of pre-stressed slatted floors2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study investigates the mechanical differences between old and newly produced slatted floors through a four-point bending test. To understand to what extent the actual environment has affected the slatted floors, the carbonation depth and corrosion will be examined. The tests showed no mechanical differences between slatted floors which had been in service for a certain amount of years and newly produces ones. Corrosion could be observed on some of the samples but it was not because of the carbonation process. When comparing the calculations of reinforced and pre-stressed concrete slatted floors, the result showed that the pre-stressed floor could carry up to double the load of what the reinforced slatted floor could. The conclusion of this study is, that the pre-stressed slatted floors will certainly hold for at least thirty years and will most likely hold for many years to come.

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  • 174.
    Hochreiner, G.
    et al.
    Vienna University of Technology, Austria.
    Füssl, J.
    Vienna University of Technology, Austria.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Eberhardsteiner, J.
    Vienna University of Technology, Austria.
    Influence of Wooden Board Strength Class on the Performance of Cross-laminated Timber Plates Investigated by Means of Full-field Deformation Measurements2014In: Strain, ISSN 0039-2103, E-ISSN 1475-1305, Vol. 50, no 2, p. 161-173Article in journal (Refereed)
    Abstract [en]

    Although cross-laminated timber (CLT) plates are increasingly used in high-performance building structures, a tailored composition of them or, at least, a performance-based classification scheme is not available. Especially, the influence of the quality of the ‘raw’ material (wooden boards) on the load carrying capacity of CLT elements is hardly investigated yet. For this reason, within this work, bending tests on 24 CLT plates consisting of wooden boards from three different strength classes have been carried out. The global mechanical response as well as the formation of failure mechanisms were investigated, including a full-field deformation measurement system, which allowed for a qualitatively as well as quantitatively identification of board failure modes. Interestingly, no influence of the board strength class on the elastic limit load of the CLT plates was observed, but the situation was different for the load displacement history beyond the elastic regime, where basically, two different global failure mechanisms could be distinguished. The obtained knowledge about the ‘post-elastic’ behaviour of CLT plates may serve as a basis for the optimisation of CLT products and the development or improvement of design concepts, respectively. Moreover, the obtained large ‘post-elastic’ capacity reserve of CLT consisting of high quality boards could lead to a better utilisation of the raw material.

  • 175.
    Hochreiner, Georg
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Structural behaviour and design of dowel groups: experimental and numerical identification of stress states and failure mechanisms of the surrounding timber matrix2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 131, p. 421-437Article in journal (Refereed)
    Abstract [en]

    Dowel-type fasteners in combination with steel plates are widely used in engineered timber structures. Since dowel groups are designed as semi-rigid connections subjected to an arbitrary set of internal forces, the corresponding structural behaviour of the surrounding timber matrix must be considered in the design process accordingly, including the effect of reinforcements. Corresponding stress states and failure mechanisms in the timber matrix of dowel groups are discussed herein. Surface strain fields from tests of dowel groups under complex loading situations were used to identify the sequence of cracking, as well as to assign the related failure modes. First cracking events were caused by stress peaks at the most loaded dowels and by a combination of shear stresses and stresses perpendicular to the grain, while later crack- ing events were associated with a predominant action of individual stress components. Thus, the non- linear global moment-relative rotation behaviour of dowel groups could be related to failure mechanisms in the surrounding timber matrix. The corresponding strain state was qualitatively as well as quantita- tively reproduced by means of a numerical model, which gave access to stresses in the timber matrix and has potential to be implemented as a sub-model in engineering design software. The numerical model supported the feasibility of a decomposition of the stress state due to the global bending moment into stresses caused by a couple of equal forces parallel and perpendicular to the grain, which could be used in the design process. Based on experimental and numerical findings, essential aspects for a design procedure for the timber matrix in dowel groups loaded by a combination of internal forces are proposed. 

  • 176. Hochreiner, Georg
    et al.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Schweigler, Michael
    Esser, Gerold
    Hagmann, Stefan
    Glatz, Bernhard
    The Historic Roof Structure of the Spanish Riding School in Vienna: Structural Assessment2015In: Proceedings of the International Conference on Structural Health Assessment of Timber Structures, SHATIS15, Dolnoslaskie Wydawnictwo Edukacyjne (DWE) , 2015, p. 248-259Conference paper (Refereed)
    Abstract [en]

    In 2012, the historical roof structure of the Spanish Riding School, built in the years from 1729 to 1735 as part of the ensemble of the Vienna Imperial Palace (called Hofburg), was documented by students and staff of the Vienna University of Technology. The survey was performed deformation- accurate and included both, the main structure and corresponding joints. Consequently, the documentation highlights deviations from the initial perception of the roof structure such as broken joints, inactivity of compressive devices like knee braces or excessive displacements of single structural members. Probably, these damages led to strengthening measures (=additional substructures) that were added in recent times to avoid progressive failure. This documentation formed the basis for the assessment of this historical roof structure from a structural and timber engineering point of view, which will be presented herein. The focus of the structural modelling was placed on the assessment of the two initial structural concepts, namely the main hall with and without the timber dome structure that was added in 1734, by visualisation of the internal forces and displacements. For this purpose, the nonlinear load carrying capacities and failure modes of the carpentry joints were assessed. Subsequently, alternative structural systems could be found by iterative recalculation revealing the capabilities for redundancy of the timber roof structure. Corresponding results were checked again with in-situ observations. Consequently, the findings of this study highlight the benefits of integrating modern structural and timber engineering methods and tools in the context of building history and building survey.

  • 177.
    Hoehler, Matthew
    et al.
    NIST National Institute of Standards and Technology, USA.
    Su, Joseph
    National Research Council of Canada.
    Lafrance, Pier-Simon
    National Research Council of Canada, Canada.
    Bundy, Matthew
    NIST National Institute of Standards and Technology, USA.
    Kimball, Amanda
    Fire Protection Research Foundation, USA.
    Brandon, Daniel
    RISE Research Institutes of Sweden.
    Östman, Birgit
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Fire Safety Challenges of Tall Wood Buildings: Large-scale Cross-laminated Timber Compartment Fire Tests2018In: SiF 2018– The 10th International Conference on Structures in FireFireSERT, Ulster University, Belfast, UK, June 6-8, 2018, New University of Ulster, 2018Conference paper (Refereed)
    Abstract [en]

    This study investigates the contribution of cross laminated timber (CLT) building elements to compartment fires. Six compartments (9.1 m long × 4.6 m wide × 2.7 m high) were constructed using 175 mm thick 5‑ply CLT structural panels and fire tested using residential contents and furnishings to provide a fuel load density of 550 MJ/m2. The results show that gypsum board can delay or prevent the involvement of the CLT in the fire, and that the ventilation conditions and exposed surface area of the CLT play a decisive role in the outcome of the test. The results highlight the need to use heat-resistant adhesives in cross laminated timber to minimize delamination.

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  • 178.
    Holmberg, Kristian
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Svensson, Jacob
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Anslutningar för sammansättning av flera moduler i KL-trä till ett bostadshus2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The modules currently manufactured are usually based on traditional wood frameconstruction. On the other hand, it is possible to manufacture modules in CLTinstead. The goal of the work is to design connections subjected to vertical andhorizontal load and design the connections so that a rational assembly of CLTmodulesis possible. Connections intended to be designed are from module tofoundation and from module to module. Literature survey, site visits and interviewsform the basis of the choice of attachment method. The proposal results in joints withsteel sheet and dowels, bevel screw, and single surface spline. In future projects withmodules in CLT, this work can be used as a basis for connection methods.

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  • 179.
    Hosseini Moghadam, Seyed Mazdak
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Alshihabi, Mohamed
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Mechanical behavior of a bio-based composite: influences of production conditions2016Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Some mechanical properties of DuraPulp, a bio-based, bio-degradable composite made from polylactic acid (PLA) and pulp fibers, were determined. Focus was put on the conditions during productions whereby three different press times were studied. Additionally, two different material compositions (PLA to fiber ratios) were used. Uniaxial tensile tests with two different load rates, one and 50 mm/min, were performed. An increase in maximum strength and E-modulus of DuraPulp was observed by increasing the press time, while PLA content decreased the maximum strength and E modulus.

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    Mechanical behavior of a bio-based composite
  • 180.
    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
  • 181.
    Hu, Min
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Studies of the fibre direction and local bending stiffness of Norway spruce timber: for application on machine strength grading2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Machine strength grading is a production process in the sawmill industry used to grade sawn timber boards into different strength classes with specific characteristic values of the bending strength, modulus of elasticity (MOE) and density. These properties are called grade determining properties. Each of these is predicted on the basis of a statistical relationship between the property and a so-called indicating property (IP), which is based on non-destructively assessed board properties. In most cases, the prediction of strength is crucial for the grading. The majority of commercial grading machines rely on a statistical relationship of strength to an IP, which is either a global dynamic MOE or an averaged flatwise bending MOE measured over a board length of about one meter. The problem of today’s machine strength grading is that the accuracy of the strength prediction is rather poor with a coefficient of determination of about R2 ≈ 0.5 − 0.6. One consequence of this is that much of the strength potential of timber is unused.

    The intention of this research is to contribute to a long-term goal, which is development of a method for prediction of bending strength that is more accurate than the methods available today. The research relies on three hypotheses. First, accurate prediction of bending strength can be achieved using an IP that is a localized MOE value (determined over a short length) that represents the lowest local bending stiffness of a board. Second, knowledge of the local bending stiffness with high resolution along a board’s longitudinal direction can be established on the basis of fibre direction within the board in combination with dynamic MOE. Third, fibre directions in the interior of a board can be determined by application of fibre angle models utilizing data of fibre directions on the board’s surfaces obtained from tracheid effect scanning. Following these hypotheses, this work has included laboratory investigations of local material directions, and development of models for fibre directions of the interior of boards. The work also included application of one-dimensional (1D) analytical models and three-dimensional (3D) finite element models of individual boards for the mechanical behaviour, analysis of mechanical response of boards based on experiments and based on the suggested models. Lastly, the suggested models were evaluated by comparisons of calculated and experimentally determined local bending stiffness along boards, and of predicted and experimentally determined bending strength.

    The research contributes with in-depth knowledge on local fibre directions close to knots, and detailed information on variation of the local bending stiffness in boards. Moreover, fibre angle models for fibre directions in the interior of boards are presented. By application of the fibre angle models in the 3D model of the whole board, the local bending stiffness along timber boards can be determined over a very short length (l < 50 mm). A comparison with results determined on an experimental basis show a very close similarity implying that the applied models are sufficient to capture the variation of local bending stiffness, caused by knots and fibre distortions, with very high accuracy. Furthermore, it is found that by means of IPs derived using the suggested models, bending strength can be predicted with high accuracy. For a timber sample comprising 402 boards, such IPs results in coefficient of determination as high as R2 = 0.73. However, using IPs based on the 3D finite element model did not improve the R2 value achieved when using the IPs based on the 1D model.

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  • 182.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Briggert, Andreas
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Säll, Harald
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Growth layer and fibre orientation around knots in Norway spruce: a laboratory investigation2018In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 52, no 1, p. 7-27Article in journal (Refereed)
    Abstract [en]

    The strength of structural timber largely depends on the occurrence of knots and on the local material directions in the surroundings of such knots. There is, however, a lack of methods for establishing a full dataset of the local material directions. The present research aims at the development and application of a laboratory method to assess the geometry of growth layers and the orientation of fibres in a high-resolution 3D grid within wood specimens containing knots. The laboratory method was based on optical flatbed scanning and laser scanning, the former resulting in surface images and the latter, utilizing the tracheid effect, resulting in in-plane fibre angles determined in high-resolution grids on scanned surfaces. A rectangular solid wood specimen containing a single knot was cut from a tree in such a way that it could be assumed that a plane of symmetry existed in the specimen. By splitting the specimen through this plane through the centre line of the knot, two new specimens with assumed identical but mirrored properties were achieved. On one of the new specimens, the longitudinal-radial plane was subsequently scanned, and the longitudinal–tangential plane was scanned on the other. Then, by repeatedly planing off material on both specimens followed by scanning of the new surfaces that gradually appeared, 3D coordinate positions along different growth layers and 3D orientation of fibres in a 3D grid were obtained. Comparisons between detected fibre orientation and growth layer geometry were used for the assessment of the accuracy obtained regarding 3D fibre orientation. It was shown that the suggested method is well suited to capture growth layer surfaces and that it provides reliable information on 3D fibre orientation close to knots. Such knowledge is of great importance for understanding the properties of timber including knots. The quantitative data obtained are also useful for calibration of model parameters of general models on fibre orientation close to knots.

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  • 183.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Briggert, Andreas
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Säll, Harald
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Three dimensional growth layer geometry and fibre orientation around knots: a laboratory investigation2016In: Proceedings of WCTE 2016 World Conference on Timber Engineering / [ed] Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Vienna: Vienna University of Technology , 2016Conference paper (Refereed)
  • 184.
    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.

  • 185.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Local bending stiffness for prediction of bending strength: Evaluation of models and conceptManuscript (preprint) (Other academic)
  • 186.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    An Application of 3D Fiber Angles Identified through Laser Scanning Based on Tracheid Effect2015Conference paper (Refereed)
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  • 187.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Modelling local bending stiffness based on fibre orientation in sawn timber2018In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, no 6, p. 1605-1621Article in journal (Refereed)
    Abstract [en]

    Strength of structural timber depends to a high degree on the occurrence of knots and on the local fibre deviation around such defects. Knowledge of local fibre orientation, obtained by laser scanning, has been utilized in a previously developed machine strength grading method, but rather crude assumptions regarding the fibre orientation in the interior of boards and a mechanical model that does not capture the full compliance of knotty sections were adopted. The purpose of the present study was to suggest and verify a model with which local bending stiffness can be predicted with high accuracy. This study included development of a model of fibre orientation in the interior of boards, and application of a three-dimensional finite element model that is able to capture the compliance of the board. Verification included bending of boards in the laboratory and application of digital image correlation to obtain strain fields comparable to those obtained by finite element simulation. Results presented comprise strain fields of boards subjected to bending and calculated bending stiffness profiles along boards. Comparisons of results indicated that the model suggested here was sufficient to capture the variation of local bending stiffness along boards with very high accuracy.

  • 188.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Serrano, Erik
    Lund University.
    Assessment of a Three-Dimensional Fiber Orientation Model for Timber2016In: Wood and Fiber Science, ISSN 0735-6161, Vol. 48, no 4, p. 271-290Article in journal (Refereed)
    Abstract [en]

    Wood is an orthotropic material with very different properties along and across fibers, and every board has its own pattern of knots and fiber deviations. Therefore, detailed knowledge of the three-dimensional (3D) fiber orientation of individual boards would enable more accurate assessment of properties such as stiffness, strength, and shape stability. This paper presents a method for modeling 3D fiber orientation of side boards of Norway spruce. The method is based on dot laser scanning and utilization of the tracheid effect, and it is verified by a comparison between strain fields calculated on the basis of the fiber orientation model and corresponding strains determined using digital image correlation (DIC) technique. By means of the method, it is possible to identify knots and to reproduce the fiber orientation in clear wood in the vicinity of knots. Fiber orientation models of side boards including traversing edge knots were established and integrated in finite element models of boards used for simulation of four-point bending tests. The same boards were also tested in laboratory and displacement fields of the wide faces were recorded at different load levels using DIC technique. Comparisons of strain fields from measurements and simulations showed close agreement, regarding both strain patterns and strain levels. Local strain concentrations caused by very small defects were detected using the models and also found from the laboratory test results. The modeling approach may be used both to achieve improved accuracy of existing machine strength grading methods and, after further development, also for more advanced analysis of eg crack propagation and strength of timber.

  • 189.
    Huang, Qibin
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Joy, Anitha
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Compression perpendicular to the grain of Cross-Laminated Timber: Influence of support conditions of CLT on compressive strength and stiffness2018Independent thesis Advanced level (degree of Master (One Year)), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Cross-Laminated Timber (CLT) has recently become a popular construction material for building timber structures. One advantage of CLT is, that it can be used as floor, beam and wall element. As the arrangements of layers in CLT is in perpendicular direction to each other, it exhibits remarkable strength properties in both in-plane directions. However, the low stiffness and strength properties in compression perpendicular to the grain hinder application of CLT in high rising building, since forces are usually transferred from the wall elements through floor elements perpendicular to the grain. Thus, the aim of this thesis is to get a thorough understanding of the mechanical properties of such connections for different setups, including wood-wood connections, connections with acoustic layers and connections with screws. In addition, the wall was place at different positions on the CLT-floor element. Mechanical tests and numerical simulations, by means of finite element modelling (FEM) were carried out. CLT floor elements, consisting of 5-layers, were loaded by 3-layered CLT wall elements. Displacement and deformation were continuously measured by Potentiometers/LVDTs and an optical measurement system, respectively. Based on the experimental results compressive strength, slip curve and stiffness of the CLT connections were evaluated. Subsequently, results from FE-modelling were compared with experimental findings, which show a good agreement in elastic stiffness. Experimental results exhibited a pronounced influence of the wall position and connection setup on strength and stiffness. Central position of the wall showed higher mechanical properties than edge position. Highest strength and stiffness were found for screwed connections, where the wood-wood connections showed similar results. Connections with acoustic layers exhibited the lowest mechanical properties.

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  • 190.
    Hultinsson, Petter
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dikta, Adrian
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Undersökning för att göra en byggnad mer energieffektiv: en fallstudie2020Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    There are today many buildings in Sweden that were built during a time when energy use was not considered a problem and thus did not have the same energy performance requirements as we have today. Therefore, in renovation, it is important to consider energy-efficient solutions. Studies show that it is possible to reduce the energy consumption of a building by 36-54 % through renovations, however, it is not always profitable when using a LCC-analysis.The study conducted by modeling and site visits to a multi-family housing with excessive energy use has been designed to reduce this through proposed measures. The results show that the installation of heat recovery and improvement of the building envelope have a major effect on the energy performance of the house. It has also been observed that the resident’s impact on the energy balance can be difficult to estimate, in which the study had problems to theoretically gaining the same energy consumption as the energy declaration shows.The proposals that are recommended are installation of heat recovery, solar cells, individual measurement and billing (IMD) and window/door seals as these are profitable according to the LCC analysis. With proposed measures, energy consumption has been reduced from 173 to 114 kWh/m2 per year, a reduction of 34 %.

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  • 191.
    Hultman, Matilda
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Kartläggning av energianvändning och beräkning av kallras vid fönster i en kulturhistoriskt värdefull byggnad2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Energianvändningen i världen har ökat kraftigt de senaste åren och byggnadssektorn är bidragande faktor till den ökningen. Byggnadssektorn står idag för närmare 40% av den totala energianvändningen och för en tredjedel av utsläppen av växthusgaser. För att minska energianvändningen och påverkan på klimatet finns stora vinster att hämta genom att energieffektivisera de befintliga byggnaderna.  

    De kulturhistoriska byggnaderna utgör en viktig del av det befintliga byggnadsbeståndet. Vid renovering av dessa byggnader måste hänsyn tas dels till energieffektivisering men även till det kulturhistoriska värdet hos byggnaden. Något som i dag kan vara ett komplext problem.

    Energiprestandan i en byggnad är väl förknippad med inomhusklimatet. Obehagligt inomhusklimat kan orsakas av flera anledningar. En anledning kan vara från kalla ytor i ett rum, då drag i form av kallras skapas. För att motverka drag i form av kallras krävs mer energi för att värma upp luften.

    Målet med studien är att kartlägga energianvändningen och dess förluster i en kulturhistoriskt värdefull byggnad belägen i Växjö. Samt att beräkna det kallras som uppstår i byggnadens djupa fönsternischer.

    Kartläggning av byggnaden görs i datorsimuleringsprogrammet VIP+ utifrån uppmätta värden från byggnadens ritningar. I programmet byggs även tvådimensionella konstruktionsdelar av fönsteranslutning i yttervägg upp som sedan används till beräkning av kallras. Kallraset beräknas med hjälp av ekvationer som Per Heiselberg har tagit fram tillsammans med de värden som kan avläsas i VIP+.

    Resultat av energisimuleringen visar att de största energiförlusterna sker genom transmission i klimatskalet, dvs 76 %. Resultatet visar även att kallraset som skapas i fönsterdörrarnas nisch inte uppfyller kraven från Folkhälsomyndigheten på luftrörelse under 0,15 m/s inom vistelsezonen när temperaturen understiger ca 0 oC. 

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  • 192.
    Humbla, Madelene
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Näslund, Linn
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Identitet - skillnader i karaktär: Beskriver hur ett bostadsområde kan gestaltas2014Independent thesis Basic level (degree of Bachelor), 180 HE creditsStudent thesis
    Abstract [sv]

    Syftet med arbetet är att ta reda på om det går att bygga fram identitet. Även att ta fram ett förslag som uttrycker identitet.

    Två aspekter som är viktiga för att skapa ett välmående bostadsområde är identitet och karaktär. Områdens identitet handlar om struktur och strukturen behöver vara unik och igenkännbar. Identitet ska spegla något som är minnesvärt för platsen. De faktorer som påverkar skapelsen av positiv identitet tas upp i teorikapitlet. Där studeras bland annat byggnadens utformning, materialval samt ljusinsläpp men också byggnadernas omgivande miljö och hur grönområden påverkar människans hälsa. Samspelet mellan byggnader och utemiljön studeras också. Förslaget ritas som en visualiseringsmodell där identiteten avgränsas till den yttre miljön där utformningen på byggnaderna och omgivningen studeras.

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    Identitet
  • 193.
    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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  • 194.
    Ismail, Eman
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Distribution of stresses and displacements in skewed concrete slabs2017Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    A 3D nonlinear finite element analysis was developed for simulating the behavior of skewed concrete slabs and to identify the response of the slab with different angles and element sizes. The purpose of this research is helping the engineering and construction industry to utilize the FEM study and results more in different structural applications.Simulations performed in ABAQUS for skewed slabs are also compared to straight and skewed slabs according to the analytical formulation by Timoshenko.The result showed that when the distance increases, the load capacity measured by reaction forces decreases for all different skew angles except angle 0° and 15° which show a stable reaction force along the entire path. .The study reveals that depending on the skew angle and the element size, the stress distribution and vertical displacements in the slab vary significantly from those in a straight slab. It is shown that the displacement decreases with the increase of the skew angle while the stresses increase with the decrease of the skew angle.There are small differences in the vertical displacements and stress distribution between the results obtained by this study and the results obtained by Timoshenko regarding the plates with skews of 0°, 30° and 45°.

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  • 195.
    Israelsson, Simon
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Hallgren, Anton
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Ventilation i flerbostadshus- hur fungerar den ur ett fuktperspektiv?2018Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    To create a good indoor climate in apartment buildings, high demands are made on the ventilation system to take care of the moisture that is created. There is therefore reason to investigate if Boverket, the Swedish National Board of Housing, Building and Planning, requirements for minimum airflow are sufficient from a moisture point of view. The purpose is to rise awareness about increasing additional moisture in newly built apartment buildings, which could change the project planning of ventilation systems in the future. In order to investigate whether requirements of the Boverket building regulations are sufficient from a moisture point of view, relative humidity and additional moisture were analyzed in four apartment buildings in Jönköping. Several apartments received high values of additional moisture and relative humidity which could damage the building and affect human health. The requirements of Boverket building regulations for minimum airflow should therefore be reviewed.

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  • 196.
    Jagerborn, Sandra
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Moqvist, Gunnar
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Energikartläggning av kvarteret Körsbäret: med fokus på kulvertförluster2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Sveriges regering har antagit tydliga mål för minskad energianvändning i bostadssektorn. En energikartläggning av bostadsområdet kvarteret Körsbäret i Växjö utförts. Området är byggt år 1962, hus från en tid som idag har stor potential för energieffektivisering. I nuvarande värmesystem är en fjärrvärmecentral placerad i ett av husen och betjänar även via markkulvertledningar de tre övriga huskropparna med värme och tappvarmvatten. En simulering om det skulle bli energi- och kostnadseffektivt att byta ut kulvertledningarna mot nya alternativt att förlägga en fjärrvärmecentral i varje huskropp har utförts.

    Energikartläggningen visade på stor variation av den specifika energianvändningen för området och att inget av husen uppfyllde dagens krav för nybyggnation i BBR på 80 kWh/m2Atemp och år. Dock låg energianvändningen klart under genomsnittet för flerbostadshus byggda under 1960-talet.

    Simuleringen visade att ett byte av kulvertledningar skulle medföra stora energibesparingar, vilket också resulterade i att detta alternativ hade den lägsta livscykelkostnaden. 

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  • 197.
    Jarnerö, Kirsi
    et al.
    Technical Research Institute of Sweden, SP Wood Technology, Vidéum Science Park,Växjö.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vibration properties of a timber floor assessed in laboratory and during construction2015In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 82, p. 44-54Article in journal (Refereed)
    Abstract [en]

    Natural frequencies, damping ratios and mode shapes of a prefabricated timber floor element have been assessed experimentally in laboratory with different boundary conditions and in situ (in field) at different stages of construction. In laboratory the change in modal parameters was studied with free-free boundary conditions and simply supported on two sides. Three different simply supported tests with changes in boundary conditions were carried out; the floor placed on the support without any fastening or interlayer between support and floor, the floor screwed to the supports and the floor placed on an elastic interlayer between support and floor. The in situ tests were carried out first on the single floor element and then on the entire floor of the room into which the floor element was built in. The damping ratio of the floor increased from 1% to 3% when simply supported in laboratory to approximately 5% when placed upon a polyurethane interlayer (Sylodyn) in situ, and to approximately 6% when fully integrated in the building. Thus the in situ conditions have considerable influence on the damping and the values assessed are very high in comparison with damping values suggested in design codes. Regarding natural frequencies it was concluded that the major change in these occur as the floor element is coupled to the adjacent elements and when partitions are built in the studied room, the largest effect is on those modes of vibration that are largely constrained in their movement.

  • 198.
    Jarnerö, Kirsi
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Simmons, C
    Bard, V
    Vibration performance of lightweight floors in multifamily houses: Resident survey and field measurementManuscript (preprint) (Other academic)
  • 199.
    Jensen, Jorgen L.
    et al.
    Univ Auckland, New Zealand.
    Quenneville, Pierre
    Univ Auckland, New Zealand.
    Girhammar, Ulf Arne
    Luleå Univ Technol.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Brittle Failures in Timber Beams Loaded Perpendicular to Grain by Connections2015In: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 27, no 11, article id 04015026Article in journal (Refereed)
    Abstract [en]

    A state-of-the-art review of simple analytical fracture mechanics models for calculation of the splitting capacity of timber beams loaded perpendicular to the grain direction by connections is presented. It is shown that most of the already available models are closely related and appear naturally as special cases of the most general model available. A new model, which is a semiempirical extension of an existing model based on a beam-on-elastic-foundation theory, is proposed. The so-called van der Put model, which forms the theoretical basis for the splitting equations used in the European and Canadian timber design codes, appears as a special case of the proposed model. The treatment of the splitting problem in some major timber design codes is reviewed and discussed based on the theoretical models and new test results. The approach used in the European timber design code where the maximum shear force on either side of a connection is considered rather than the total load applied on a connection is not in agreement with the test results presented. While the European and Canadian timber design codes apply a constant value for a material property related to the splitting performance irrespective of the material considered, the presented experimental results indicate that the material property for Radiata pine laminated veneer lumber can be close to twice the value for Douglas fir glulam. The presented test results also show that despite the fact that Douglas fir glulam has a significantly higher mean perpendicular-to-grain tensile strength than Radiata pine laminated veneer lumber, the splitting failure load of Radiata pine laminated veneer lumber is nevertheless significantly higher than that of Douglas fir glulam. The latter finding seems to be in disagreement with the German timber design code, according to which the splitting strength is proportional to the perpendicular-to-grain tensile strength. (C) 2015 American Society of Civil Engineers.

  • 200.
    Jensén, Nils
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Alfsson, Sofia
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vad tjänar att hyckla,tids nog får man cykla: Att skapa goda förutsättningar för cykeltrafiken på Växjö stationsområde2014Independent thesis Basic level (degree of Bachelor), 180 HE creditsStudent thesis
    Abstract [sv]

    Detta arbete syftar till att utreda vilka faktorer som möjliggör ökade flöden av cykeltrafik på Växjö stationsområde. Arbetets genomförandemoment utgår i aktuell teori och forskning inom området.

    Utifrån Växjös ambitiösa miljömål och vilja att skapa goda förutsättningar för cyklister (tillsammans med projektledningens önskemål om förslag på detta) bedöms ett stort behov finnas av att hitta lämpliga platser för nya cykelparkeringar och en byggnation av ett nytt cykelgarage. Placeringen för cykelgaraget kommer att utgå från de visioner och planer som finns för tidigare nämnd ombyggnation på Växjö stationsområde.

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    Rapport
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