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  • 1. Epmeier, Hannah
    et al.
    Johansson, Marie
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Kliger, Robert
    Westin, Mats
    Bending creep performance of modified timber2007In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 65, no 5Article in journal (Refereed)
    Abstract [sv]

    The present study is a supplement to Epmeier and Kliger (2005), which investigated the effect of three different modification methods (acetylation, modification with methylated melamine resin and heat treatment in vegetable oil) on four material properties (density, modulus of elasticity (MOE), creep deflection and relative creep) and their inter-relations. In this study, another modification method (furfurylation) and four additional material parameters (“relative stiffness”, i.e. MOE/density, moisture content, change in moisture content and anti-creep efficiency) and their correlations are included. In addition, the creep curves were analysed to assess the development of bending creep performance. The properties were assessed by experimental work on 132 specimens of Scots pine sapwood with dimensions of 45×70×1100 mm3. It was found that modification leads to significant changes in material properties. Furfurylation increases density and reduces creep deflection, relative creep and moisture content. Modified timber tends to deflect and creep significantly less than untreated timber. However, the extent of reduction in relative creep appears not to be related to the extent of reduction in creep deflection. Initial deflection and/or modulus of elasticity are suitable for predicting the creep deflection of untreated and modified timber.

  • 2.
    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.

  • 3.
    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.

  • 4.
    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. Linnaeus University, Faculty of Technology, Department of Built Environment and Energy 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, 2016Conference paper (Refereed)
  • 5.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Olsson, Anders
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Bengtsson, Charlotte
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Grading of sawn timber using the vibration technique: locating imperfections based on flexural mode shapes2011In: 17th international nondestructive testing and evaluation of wood symposium / [ed] Ference Divos, Sopron, Hungary: University of West Hungary , 2011, p. 269-276Conference paper (Refereed)
    Abstract [en]

    The present study aims at investigating the potential of using mode shape or mode shape curvature (MSC) for detecting defects in wooden beams. It includes modal analysis, Finite Element (FE) modeling and visual scanning. An FE model was created to investigate the effect of defects of different size and location on the mode shape/MSC. The mode shape/MSC showed a good potential to be used for finding defects. An experimental study on 17 boards of Norway spruce, dimensions of 50×150×3900 mm, was conducted using experimental modal analysis. The findings reveal that: (1) the mode shape/MSC studied in the FE-model could be used to locate defects, (2) the method is very sensitive to measurement noise and it requires an accurately measured mode shape, (3) an error analysis shows that it is not possible to achieve the accuracy needed using accelerometers.

  • 6.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Comparison of local variation of modulus of elasticity determined on basis of scanned fiber angles and full strain field measurements2013In: The 18th International Nondestructive Testing and Evaluation of Wood Symposium, Madison, WI, USA, 2013Conference paper (Refereed)
    Abstract [en]

    Strength grading methods are normally based on relationships between one measured value of modulus of elasticity (MOE), regarded as being valid for the whole board, and bending strength. Studies have shown, however, that with a detailed knowledge of local variation of MOE within boards, a highter coefficient of determination (R2) with respect to bending strength can be obtained. Measurements of fiber angles from laser scanning has shown to be a powerful tool to establish MOE profile along boards in a speed that cooresponds to the production speed at a sawmill. The present study aims at investigating the accuracy of the local MOE profile determined on basis of fiber angles from laser scanning. The study was carried out on a board of Norway spruce of dimension 50 by 150 by 3,900 mm. First the fiber angles on all four surfaces were identified using a WoodEye scanner and on the basis of these measurements, a MOE profile was calculated. Thereafter, the board was subjected to a constant bending moment and suring loading an image correlation system, Aramis, was employed for detection of the strain field with high resolution along the whole board. This strain field was then used to estanlish a 'true' MOE profile along the board. The MOE profiles determined in two different ways were compared and they show a close compliance. However, some difference were found and these were used for calibration of the method for MOE determination on the basis of scanning results. The present research thus contributes further improvement of a newly suggested grading method.

  • 7.
    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.

  • 8.
    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)
  • 9.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology. Linnaeus University, Faculty of Technology, Department of Built Environment and Energy 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.

  • 10.
    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.

  • 11.
    Högberg, Karl-Anders
    et al.
    Skogforsk.
    Hallingbäck, Henrik
    SLU.
    Säll, Harald
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Jansson, Gunnar
    Skogforsk.
    The potential for the genetic improvement of sawn timber traits in Picea abies2014In: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 44, no 4, p. 273-280Article in journal (Refereed)
    Abstract [en]

    This study evaluated the potential for the selective genetic improvement of the structural quality traits important in sawn Norway spruce (Picea abies (L.) Karst.) timber based on early and nondestructively assessed field traits. From a 34-year-old Norway spruce trial situated in southern Sweden, 401 butt logs were sampled and sawn to produce two 50 × 100 mm boards that were dried to an 18% moisture content. Structural quality traits were assessed, and genetic parameters were estimated, including additive genetic variance, heritability, and their genetic correlations with field traits. Board twisting, density, and modulus of elasticity (MOE, stiffness) were found to have appreciable heritabilities (0.23–0.44). Board twist was found to have a strong genetic correlation with grain angle measured under bark in the field (0.93), and both board MOE and density exhibited strong genetic correlations with field-assessed pilodyn penetration (–0.75 and –0.91, respectively). Although these observations were made on a thinning material comprising mainly juvenile wood, they nonetheless suggest grain angle and pilodyn penetration to be promising candidates as selection criteria for Norway spruce breeding. Heritabilities of other sawn timber traits were lower and the genetic correlations between these traits and field traits were also lower, variable, and had large estimation errors.

  • 12.
    Johansson, Marie
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Al-Emrani, Mohammad
    Jacob, Jubin
    Garzon Barragan, Olga
    Crocetti, Roberto
    Increased stiffness of timber beams with steel and/or CFRP laminates2007In: Proceedings of third international conference on structural engineering, mechanics and computation, 2007Conference paper (Refereed)
  • 13.
    Johansson, Marie
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Lassl, Victor
    Löfgren, Patrick
    Engström, Björn
    Kliger, Robert
    Standardised information flow for connections in industrialised construction2007In: Proceedings of ManuBuild 1st International Conference - The Transformation of the Industry: Open Building Manufacturing, CIRIA, Classic House, London , 2007Conference paper (Refereed)
    Abstract [en]

    The ideal open building system is a vision that the building industry should aim at. It means a system that

    combines the industrial efficiency with the traditional flexibility. Such a system would mean individual designs,

    built up with different elements that could be bought from any producer around the world, connected to each

    other with connections from different producers. Even more challenging would be to have components that are

    flexible, compatible with each other and interchangeable at a later date.

    In order for manufacturers of different components to be able to sell their products to a large number of

    contractors; flexible, integrated connections are needed, that also are very easy to use during assembly and are

    cheap and effective to produce. To make this possible it is necessary to find a way to communicate connection

    features and requirements in an easy manner.

    The aim of this paper is to show two strategies, i.e. design-based strategy and function-based strategy, analyse

    them and to produce guidelines on further development of such strategies. The question is which strategy is best

    suited to be used when working with open building systems.

    The final output is the idea of the standardisation of information; the Part Request Form with which the

    performance of connections in term of specifications could be communicated so that it is understandable for

    everyone, from the system owner to the manufacturer of connections.

  • 14.
    Johansson, Marie
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Bolmsvik, Åsa
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Jarnerö, Kirsi
    SP Hållbar samhällsbyggnad.
    Olsson, Jörgen
    SP Hållbar samhällsbyggnad.
    Reynolds, Thomas
    University of Cambridge, UK.
    Building higher with light-weight timber structures: the effect of wind induced vibrations2015In: Proceedings of the Internoise 2015 conference, Society of Experimental Mechanics (SEM) , 2015Conference paper (Refereed)
  • 15.
    Johansson, Marie
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Jarnerö, Kirsi
    SP Sveriges tekniska forskningsinstitut.
    Landel, Pierre
    SP Sveriges tekniska forskningsinstitut.
    Tall timber buildings: a preliminary study of wind-induced vibrations of a 22-storey building2016In: Proceedings of the World Conference on Timber Engineering (WCTE 2016): August 22-25, 2016, Vienna, Austria / [ed] J. Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Vienna, Austria, 2016Conference paper (Other academic)
    Abstract [en]

    During the last years the interest in multi-storey timber buildings has increased and several medium-to-high-rise buildings with light-weight timber structures have been designed and built. Examples of such are the 8-storey building “Limnologen” in Växjö, Sweden, the 9-storey “Stadthouse” in London, UK and the 14-storey building “Treet” in Bergen, Norway. The structures are all light-weight and flexible timber structures which raise questions regarding wind induced vibrations. This paper will present a finite element-model of a 22 storey building with a glulam-CLT structure. The model will be used to study the effect of different structural properties such as damping, mass and stiffness on the peak acceleration and will be compared to the ISO 10137 vibration criteria for human comfort. The results show that it is crucial to take wind-induced vibrations into account in the design of tall timber buildings.

  • 16.
    Johansson, Marie
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Mahapatra, Krushna
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Vessby, Johan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Blom, Åsa
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Expert competence for sustainable timber engineering: a master program in close cooperation between industry and academia2014In: WCTE 2014 - World Conference on Timber Engineering, Proceedings, 2014Conference paper (Refereed)
    Abstract [en]

    From a legislative point of view it has been possible to build timber buildings with arbitrary number of storeys in Sweden during almost two decades. Several buildings up to eight storeys have been completed during that time, but the competence for planning and building such structures are limited to a handful of actors. This fact has been recognized by funders of research/education and an educational program for spreading the knowledge within the industry led by Linnaeus University is financed since about two years. Particularly interesting in the programme is that the courses are developed in cooperation between the industry and the academia. The courses are to fulfil needs with respect to knowledge, but also with respect to format so that the main target group, skilled engineers within the industry, can find the motivation to follow a course or lager parts of the program.

  • 17.
    Johansson, Marie
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Olsson, Anders
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Grading of sawn timber with dynamic methods – influence of defect2010In: WCTE 2010 – The 11th World Conference on Timber Engineering, Riva del Garda, Italy, 20-24 June, 2010Conference paper (Refereed)
  • 18.
    Johansson, Marie
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Olsson, Anders
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Grading of sawn timber with dynamic methods – influence of defects2009In: Proceedings of the COST E53 Workshop, Lisbon 22-23 October 2009 / [ed] José António Santos, 2009Conference paper (Other academic)
  • 19.
    Johansson, Marie
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Ormarsson, Sigurdur
    Technical University of Denmark.
    Influence of growth stresses and material properties on distortion of sawn timber – Numerical investigation.2009In: Annals of Forest Science, ISSN 1286-4560, E-ISSN 1297-966X, Vol. 66, no 6, article id 604Article in journal (Refereed)
  • 20.
    Johansson, Marie
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Schauerte, Tobias
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Nine storey residential timber construction and the municipal strategy of the city Växjö: [ Neun Geschosse in einem Wohngebiet aus Holz und die kommunale Holzbaustrategie der Stadt Växjö ]2015In: 21. Internationales Holzbau-Forum IHF 2015, Biel: Forum-Holzbau , 2015, p. 1-10Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    Due to devastating fires in several Swedish cities between 1838 and 1843, timber was not allowed to be used any more in bearing constructions for buildings with more than two floors. In 1994, the building code was changed towards functional requirements and timber could be used again in multi storey applications. However, this 150 year lasting prohibition let to the fact that building with timber in such applications barely developed. The market and the industry were used to steel and concrete, and mostly still are. Therefore, a strategy for more wood in construction was launched and implemented by the Swedish government in 2004, a.o. aiming at increasing the competition of building materials and -techniques. Here, prefabrication in an industrialized way was highlighted. Additionally, more Swedish wood should be processed domestically to save and provide jobs, but also to meet environmental concerns about reducing the CO2 footprint (Schauerte 2009).

    Regarding the implementation of that strategy, the Minister for Communications and Regional Policy in the Ministry of Industry, Employment and Communications, Ulrika Messing, stated that regional innovators and entrepreneurs would be of utmost impor- tance to reach the set up goals. Here, Växjö municipality comes into play.

  • 21.
    Johansson, Marie
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sjödin, Johan
    A general FE-model to predict capacity of a steel-timber dowel joint with complex loading2010In: WCTE 2010 – The 11th World Conference on Timber Engineering, Riva del Garda, Italy, 20-24 June, 2010Conference paper (Refereed)
  • 22.
    Johansson, Marie
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Säll, Harald
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Lundqvist, Sven-Olof
    Innventia.
    Properties of materials from Birch – Variations and relationships: Part 2. Mechanical and physical properties2013Report (Other academic)
    Abstract [en]

    Birch regarded as Sweden’s third largest tree species. The two birch species, Silver- and Downy birch represents about 12% of total Swedish timber volume. For forestry, birch an important tree species which today mainly used for the manufacture of pulp and paper.

    The aim of this project was to describe mechanical and physical properties of birch. The properties that have been studied are stiffness, bending strength, shrinkage, spiral gran angle, density and microfibril angle in the cell wall and vessel cells, from different parts of the birch stems grown at different rates. The mapped properties have been compared also with those of other tree species, mainly spruce. The long term aim is to increase the knowledge of the birch wood properties to provide better predict their impact on products as well as provide a basis for better utilization of Swedish birch raw material and hopefully using birch as future structural timber.

    Three birch stands with different growth was chosen: Two stands where the birch growth has been different in a mixed forests stand of spruce and pine, and a fast growing stand with improved birch seedlings. Samples were taken from four different heights in the trees. The main thing that has been analyzed is the bending strength, modulus of elasticity, shrinkage coefficients in different directions and spiral grain. The mechanical tests are carried out on tines that are 20 x 20 x 300 mm and the fiber angle measurements were carried out on discs. These results have supplemented by the results of analyzes conducted with lnnventias SilviScan instruments that are able to recognize variations of year ring wood properties. Some of these are density, and microfibril angle, which is also included in this report.

    The results show that the wood from normal growth and fast growth improved birch receive equivalent wood properties. The results also show that birch wood properties are slightly better than that in Norway spruce.

    The material in this project was limited to only three stands and 11 sampled trees and therefore it can´t provide complete answers to the birch trees different wood properties. Limitations include genetic origin, growth rate, earlier silvicultural treatment and number of sample trees.

  • 23.
    Karlsson, Stefan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Jonson, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Single-Side Ion Exchange Strengthening of Holed Float Glass2012In: Nordic Conference on Ceramic and Glass Technology, 2012Conference paper (Other academic)
    Abstract [en]

    The fracture strength of oxide glasses is to a large degree influenced by other factors than the inherent strength of the bonds in the vitreous network such as surface defects. Due to the brittle nature of glass, mechanical processing decreases the strength substantially. The aim of this study was to investigate ion exchange strengthening also known as chemical strengthening of commercially available mechanically processed soda-lime-silicate float glass and to compare it with as-received float glass by means of flexural fracture load. The dimensions of the samples were 66±2 x 66±2 mm and two series had 7 mm diamond drilled holes in the centre of each sample while one series was as-received. Ion exchange of sodium ions by larger potassium ions were performed by treating the air-side of a series of samples with a KNO3:KCl mixture at 450 °C. The flexural fracture load of both untreated and ion exchanged holed samples was measured by means of the coaxial double ring test. The ion exchanged samples showed an arithmetic mean fracture load increase of approximately 140% compared to untreated holed float glass. The drilled hole decreases the arithmetic mean fracture load to approximately 25% of as-received float glass whilst the strengthening effect of the ion exchange improves it to around 65% of as-received float glass.

  • 24.
    Karlsson, Stefan
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Jonson, Bo
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    The effect of single-side ion exchange on the flexural strength of plain and holed float glass containing a drilled hole2013In: European Journal of Glass Science and Technology. Part A: Glass Technology, ISSN 1753-3546, Vol. 54, no 2, p. 66-71Article in journal (Refereed)
    Abstract [en]

    The effect of single-side ion exchange (using a KNO3:KCl mixture) on the ring-on-ring flexural strength of float glass has been studied. Two ion exchanged series, treated at 450 and 515°C, were investigated. The ion exchanged samples showed approximately 160 respectively 100% increases in their arithmetic mean strength compared to as-received float glass. Furthermore, a series of samples containing drilled holes were studied in order to investigate the effect of single-side ion exchange on such common construction elements. The samples that contained drilled holes were ion exchanged at 450°C and showed around 140% increase of the fracture load compared to the untreated samples containing drilled holes. As a general observation, the ion exchange treatment induced ~110 MPa compressive stresses (515°C) and ~180 MPa compressive stresses (450°C). The ion exchanged samples showed no significant increase in stiffness. 

  • 25. Kliger, Robert
    et al.
    Al-Emrani, Mohammad
    Johansson, Marie
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Crocetti, Roberto
    Strengthening glulam beams with steel or CFRP plates2007In: Proceedings of Asia-Pacific Conference on FRP in Structures (APFIS 2007), 2007Conference paper (Refereed)
  • 26.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Oscarsson, Jan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Dynamic excitation and higher bending modes for prediction oftimber bending strength2010In: Proceedings of the final conference of COST action E53, 2010Conference paper (Other academic)
    Abstract [en]

    The potential of utilizing eigenfrequencies corresponding to edgewise bending modes for predicting the bending strength of timber is investigated. The research includes measurements of axial and transversal resonance frequencies, laboratory assessment of density, static bending stiffness and bending strength of 105 boards of Norway spruce of dimensions 45×145×3600 mm. It is shown that Eb,1, (MOE based on the eigenfrequency of the first bending mode) gives a higher coefficient of determination to the bending strength than what Ea,1 (MOE based on the first axial eigenfrequency) does. It is also shown that eigenfrequencies corresponding to higher bending modes can be used in the definition of a new prediction variable, the modulus of inhomogeneity (MOI). This is a scalar value representing the lack of fit between the true, measured eigenfrequencies and the expected (assuming homogeneity) eigenfrequencies of a board. The results show that using the MOI as a third prediction variable, in addition to Eb,1 and density, increases the coefficient of determination with respect to bending strength from R2 = 0.69 to R2 = 0.75.

  • 27.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Oscarsson, Jan
    SP Technical Research Institute of Sweden, Videum Science Park, 351 96, Växjö, Sweden.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Prediction of timber bending strength on basis of bending stiffness and material homogeneity assessed from dynamic excitation2012In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 46, no 4, p. 667-683Article in journal (Refereed)
    Abstract [en]

    The potential of utilizing resonance frequencies corresponding to edgewise bending modes for predicting the bending strength of timber is investigated. The research includes measurements of axial and transversal resonance frequencies, laboratory assessment of density, static bending stiffness and bending strength of 105 boards of Norway spruce of dimensions 45×145×3600 mm. It is shown that Eb,1, (MOE based on the resonance frequency of the first bending mode) gives a higher coefficient of determination to the bending strength than what Ea,1 (MOE based on the first axial resonance frequency) does. It is also shown that resonance frequencies corresponding to higher bending modes can be used in the definition of a new indicating property, the measure of inhomogeneity (MOI). This is a scalar value representing the lack of fit between the true, measured resonance frequencies and the expected (assuming homogeneity) resonance frequencies of a board. The results show that using the MOI as a third indicating property, in addition to Eb,1 and density, increases the coefficient of determination with respect to bending strength from R2=0.69 to R2=0.75.

  • 28.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Oscarsson, Jan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Prediction of timber bending strength using dynamic excitation of bending modes2010In: Proceedings of the 11th World Conference on Timber Engineering / [ed] Ario Ceccotti, 2010Conference paper (Refereed)
    Abstract [en]

    The potential of utilizing eigenfrequencies corresponding to edgewise bending modes for predicting the bending strength of timber is investigated. The research includes measurements of axial and transversal resonance frequencies, laboratory assessment of density, static bending stiffness and bending strength of 105 boards of Norway spruce of dimensions 45×145×3600 mm. It is shown that Eb,1, (MOE based on the eigenfrequency of the first bending mode) gives a higher coefficient of determination to the bending strength than what Ea,1 (MOE based on the first axial eigenfrequency) does. It is also shown that eigenfrequencies corresponding to higher bending modes can be used in the definition of a new prediction variable, the modulus of inhomogeneity (MOI). This is a scalar value representing the lack of fit between the true, measured eigenfrequencies and the expected (assuming homogeneity) eigenfrequencies of a board. The results show that using the MOI as a third prediction variable, in addition to Eb,1 and density, increases the coefficient of determination with respect to bending strength from R2 = 0.69 to R2 = 0.75.

  • 29.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology. SP Technical Research Institute of Sweden.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Prediction of timber bending strength and in-member cross-sectional stiffness vartiation on basis of local wood fibre orientation2013In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 71, no 3, p. 319-333Article in journal (Refereed)
    Abstract [en]

    Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3600 mm, a coefficient of determination as high as 0.68-0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.

  • 30.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Förfarande och anordning för utvärdering av en bräda av trä2014Patent (Other (popular science, discussion, etc.))
    Abstract [sv]

    Föreliggande redogörelse avser en metod och en anordning för utvärdering av en bräda av trä med en ländriktning. Data som indikerar fiberorienteringen över brädans yta inhämtas och för ett antal underpartier hos brädan bestäms en nominell, lokal elasticitetsmodul, MOE, på basis av nämnda fiberorienteringsdata och en nominell materialparameter. En nominell global MOE i längdriktningen för träbrädan i sin helhet genereras och jämförs med en sekundär global MOE. På basis av nämnda fiberorienteringsdata och denna jämförelse genereras en uppskattad lokal elasticitetsmodul, MOE, i nämnda längdriktning för ett flertal underpartier. Dessa data kan användas för exempelvis tillförlitlig hållfasthetsgradering av träbrädor.

  • 31.
    Ormarsson, Sigurdur
    et al.
    Technical University of Denmark.
    Dahlblom, Ola
    Johansson, Marie
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Finite element study of growth stress formation in wood and related distortion of sawn timber2009In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 43, p. 387-403Article in journal (Refereed)
    Abstract [en]

    Lack of straightness in timber is the most frequent complaint regarding solid (and laminated) timber products worldwide. Nowadays, customers demand higher quality in the shape stability of wood products than they did earlier. The final distortion of timber boards is mostly caused by moisture-related stresses in wood (drying distortions) and growth-related stresses (distortions appearing when logs are split up to timber boards by sawing). To get more knowledge on how these distortions can be reduced in wooden products, there is a need for improved understanding of this material behaviour through good numerical tools developed from empirical data. A three-dimensional finite element board distortion model developed by Ormarsson (Doctoral thesis, Publ. 99:7, 1999) has been extended to include the influence of growth stresses by incorporating a one-dimensional finite element growth stress model developed here. The growth stress model is formulated as an axisymmetric general plane strain model where material for all new annual rings is progressively added to the tree during the analysis. The simulation results presented include how stresses are progressively generated during the tree growth, distortions related to the redistribution of growth stresses during log sawing, and distortions and stresses in drying reflecting the effects of growth stresses. The results show that growth stresses clearly vary during tree growth and also form a large stress gradient from pith to bark. This in itself can result in significant bow and crook deformations when logs are sawn into timber boards. The distortion results from the simulations match well with the results observed in reality. The parametric study also showed that the radial growth stress distribution is highly influenced by parameters such as modulus of elasticity, micro fibril angle and maturation strain.

  • 32.
    Ormarsson, Sigurdur
    et al.
    Technical University of Denmark.
    Dahlblom, Ola
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Numerical study of how creep and stiffness evolution affect the growth stress formation in trees2010In: Trees, ISSN 0931-1890, E-ISSN 1432-2285, Vol. 24, no 1, p. 105-115Article in journal (Refereed)
    Abstract [en]

    It is not fully understood how much growth stresses affect the final quality of solid timber products in terms of e.g. shape stability. It is for example difficult to predict the internal growth stress field within the tree stem. Growth stresses are progressively generated during the tree growth and they are highly influenced by climate, biologic and material related factors. To increase the knowledge of the stress formation a finite element model was created to study how the growth stresses develop during the tree growth. The model is an axisymmetric general plane strain model where material for all new annual rings is progressively added to the tree during the analysis. The material model used is based on the theory of small strains (where strains refer to the undeformed configuration which is good approximation for strains less than 4%) where so-called biological maturation strains (growth-related strains that form in the wood fibres during their maturation) are used as a driver for the stress generation. It is formulated as an incremental material model that takes into account elastic strain, maturation strain, viscoelastic strain and progressive stiffening of the wood material. The results clearly show how the growth stresses are progressively generated during the tree growth. The inner core becomes more and more compressed whereas the outer sapwood is subjected to slightly increased tension. The parametric study shows that the growth stresses are highly influenced by the creep behaviour and evolution of parameters such as modulus of elasticity, micro fibril angle and maturation strain.

  • 33.
    Ormarsson, Sigurdur
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Johansson, Marie
    Chalmers Konstruktionsteknik.
    Finite element simulation of growth stress formation and related board distortions resulting from sawing and forced drying2006In: New Zealand Journal of Forestry Science, ISSN 0048-0134, E-ISSN 1179-5395, Vol. 36, no 2/3, p. 408-423Article in journal (Refereed)
    Abstract [sv]

    Matching timber quality with end-user requirements is a major research issue and lack of straightness in timber is the most frequent complaint worldwide. The final distortion of timber boards is caused mostly by moisture-related deformations and growth stresses that develop during growth of the tree, but how much the growth rate and growth stresses affect the final shape stability is not fully understood. A finite element analysis in which stress development during tree growth was simulated was performed with the aim of better understanding how growth stresses are generated. The tree growth model was formulated in terms of large strain settings (large changes in volume), whereas the material model for stress development was based on the theory of small strains. An earlier three-dimensional distortion model was developed further for studying the influence of growth stresses on final distortion of the board. The results showed that growth stresses clearly vary during tree growth and they also form a large stress gradient from pith to bark. This itself can result in significant bow and crook deformation when the log is sawed into boards.

  • 34.
    Oscarsson, Jan
    et al.
    SP Sveriges Tekniska Forskningsinstitut.
    Olsson, Anders
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Serrano, Erik
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Determination of tensile strain fields in Norway spruce side boards using two master-slave connected contact-free measurement systems based on digital image correlation.2011In: Proceedings (Poster session) of the 17th International Nondestructive Testing and Evaluation of Wood Symposium, Sopron, Hungary, September 14-16, 2011., 2011Conference paper (Refereed)
    Abstract [en]

    A sample of nine Norway spruce side boards of narrow dimensions were tested in tension according to the standard EN 408. Strain fields were simultaneously measured using two master-slave connected measurement systems based on digital image correlation (DIC). Each system performed a separate measurement project measuring about 50% of the measurable length of each board and the results were combined, visualized and evaluated as one project using specific DIC software. The objectives were to investigate the possibility of measuring strain fields by use of multi-system measurements, to analyze the strain field distribution and to investigate the possibility of determining local modulus of elasticity (MOE) using strain field measurements. The results show that longitudinal strain fields were useful for identification of areas with reduced stiffness, that lateral board displacements, measured by the DIC systems, can be applied for identification of local defects, and that strain fields can be used for local MOE determination.

  • 35.
    Oscarsson, Jan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Olsson, Anders
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Serrano, Erik
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Strength grading of narrow dimension Norway spruce side boards in the wet state using first axial resonance frequency2011In: International Wood Products Journal, ISSN 2042-6445, Vol. 2, no 2, p. 108-114Article in journal (Refereed)
    Abstract [en]

    Strength grading of Norway spruce (Picea abies (L.) Karst.) side boards in the wet state was investigated. For a sample of 58 boards, density and dynamic modulus of elasticity in the axial direction, MOEdyn, were determined in the wet state. The boards were then split into two parts and the procedure of determining MOEdyn was repeated both before and after the boards were dried to a target moisture content of 12 %. Finally, tensile strength of the split boards was measured and its relationship to MOEdyn for both wet and dried split boards determined. The investigation also included an evaluation of a so called reversed lamination effect on the stiffness caused by the splitting of boards into two parts. The results show that strength grading of split boards in the wet state can give just as good results as grading performed after drying. The reversed lamination effect on the stiffness of split boards was found to be of lower order.

  • 36.
    Oscarsson, Jan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Olsson, Anders
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Serrano, Erik
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Strength grading of wet Norway spruce side boards by use of axial dynamic excitation2010In: Proceedings of the 2010 World Conference on Timber Engineering, Riva del Garda, Trento, Italy, June 20-24 / [ed] Ario Ceccotti, 2010Conference paper (Refereed)
    Abstract [en]

    Strength grading of Norway spruce side boards in the wet state was investigated. For a batch of 58 boards, densities and dynamic modulus of elasticity in the axial direction, MOEdyn, were determined in the wet state. The boards were then split into two parts and the procedure of determining MOEdyn was repeated both before and after the boards were dried to a target moisture content of 12 %. Tensile strength of the split boards was measured and its relation to MOEdyn for both split and unsplit boards determined. A so called reversed lamination effect on the stiffness caused by the splitting of boards into two parts was also evaluated. The results show that strength grading of split boards in the wet state could give just as good results as grading performed after drying. The reversed lamination effect on the stiffness of split boards was found to be of lower order.

  • 37.
    Oscarsson, Jan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Olsson, Anders
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Serrano, Erik
    Strength grading of wet Norway spruce side boards for use as laminations in wet-glued laminated beams2010In: Proceedings of the final conference of COST action E53, 4-7 May 2010, Edinburgh, Scotland, 2010., 2010Conference paper (Other academic)
    Abstract [en]

    Strength grading of Norway spruce side boards in the wet state was investigated. For a sample of 58 boards of dimensions 25×120×3000 mm3, density and dynamic modulus of elasticity in the axial direction, MOEdyn, were determined in the wet state. The boards were then split into two parts and the procedure of determining MOEdyn was repeated both before and after the boards were dried to a target moisture content of 12 %. Tensile strength of the split boards was finally measured and its relation to MOEdyn for both split and unsplit boards determined. The investigation also included an evaluation of a so called reversed lamination effect on the stiffness caused by the splitting of boards into two parts. The results show that strength grading of split boards in the wet state could give just as good results as grading performed after drying. The coefficient of determination between MOEdyn in wet and dried states was as high as R2=0.92, and the relation between MOEdyn in the wet state and tensile strength in the dried state, σt, was of the same order (R2=0.55) as the relation between MOEdyn in the dried state and σt (R2=0.52). Regarding the reversed lamination effect on the stiffness of split boards, it was found to be of low order.

  • 38.
    Phiri, Darius
    et al.
    Univ Stellenbosch, South Africa.
    Ackerman, Pierre
    Univ Stellenbosch, South Africa.
    Wessels, Brand
    Univ Stellenbosch, South Africa.
    du Toit, Ben
    Univ Stellenbosch, South Africa.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Säll, Harald
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Lundqvist, Sven-Olof
    Innventia AB, Wood & Fibre Measurement Lab, Stockholm.
    Seifert, Thomas
    Univ Stellenbosch, South Africa.
    Biomass equations for selected drought-tolerant eucalypts in South Africa2015In: Southern Forests, a journal of forest science, ISSN 2070-2620, E-ISSN 2070-2639, Vol. 77, no 4, p. 255-262Article in journal (Refereed)
    Abstract [en]

    In the water-scarce environment of South Africa, drought-tolerant eucalypt species have the potential to contribute to the timber and biomass resource. Biomass functions are a necessary prerequisite to predict yield and carbon sequestration. In this study preliminary biomass models for Eucalyptus cladocalyx, E. gomphocephala and E. grandis x E. camaldulensis from the dry West Coast of South Africa were developed. The study was based on 33 trees, which were destructively sampled for biomass components (branchwood, stems, bark and foliage). Simultaneous regression equations based on seemingly unrelated regression were fitted to estimate biomass while ensuring additivity. Models were of the classical allometric form, ln(Y) = a+x(1)ln(dbh)+x(2)ln(h), of which the best models explained between 70% and 98% of the variation of the predicted biomass quantities. A general model for the pooled data of all species showed a good fit as well as robust model behaviour. The average biomass proportions of the stemwood, bark, branches and foliage were 60%, 6%, 29% and 5%, respectively.

  • 39. Robert, Kliger
    et al.
    Mohammad, Al-Emrani
    Marie, Johansson
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Roberto, Crocetti
    Strengthening timber with CFRP or steel plates - short and long-term performance2008In: WCTE 2008 – The 10th World Conference on Timber Engineering, 2008Conference paper (Refereed)
  • 40.
    Serrano, Erik
    et al.
    Lunds tekniska högskola.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Förband och anslutningsdetaljer2016In: Limträhandbok: Del 2. Projektering av limträkonstruktioner, Stockholm: Svenskt Trä , 2016, 1, p. 198-227Chapter in book (Other academic)
  • 41. Straže, A
    et al.
    Kliger, R
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Gorišek, Z
    The influence of material properties on the amount of twist of spruce wood during kiln drying2010In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 69, no 2, p. 239-246Article in journal (Refereed)
  • 42.
    Wessels, CB
    et al.
    University of Stellenbosch, South Africa.
    Crafford, PL
    University of Stellenbosch, South Africa .
    du Toit, B
    University of Stellenbosch, South Africa.
    Grahn, T
    Innventia, Sweden.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Lundqvist, S-O
    Innventia, Sweden.
    Säll, Harald
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Seifert, T
    Univesity of Stellenbosch, South Africa.
    Lumber properties of three drought tolerant eucalyptus species grown in arid regions of south africa2015In: IUFRO Symposium: Silviculture and Management of Dryland Forests,, 2015Conference paper (Other academic)
  • 43.
    Wessels, CB
    et al.
    University of Stellenbosch, South Africa.
    Crafford, PL
    University of Stellenbosch, South Africa.
    DuToit, B
    University of Stellenbosch, South Africa.
    Grahn, T
    Innventia AB, Stockholm.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Lundqvist, S-O
    Innventia AB, Stockholm.
    Säll, Harald
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Seifert, Thomas
    University of Stellenbosch, South Africa.
    Variation in physical and mechanical properties from three drought tolerant Eucalyptus species grown on the dry west coast of Southern Africa2016In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 74, no 4, p. 563-575Article in journal (Refereed)
    Abstract [en]

    Southern Africa, and specifically its western parts is dominated by low rainfall areas, and it is expected that the rainfall in most of these parts will in future decrease further due to climate change. Woodlots of fast-growing, non-invasive tree species can provide the opportunity to produce wood and release the pressure on natural woodlands, while creating much needed income to inhabitants. Over the last two decades several trials of Eucalyptus species that could potentially withstand arid conditions were established on the South African west coast. The three most promising genotypes according to their volume growth were selected among 46 pure and hybrid species from two 20-year-old trials for further evaluation. These included 10 Eucalyptus grandis × Eucalyptus camaldulensis hybrid trees, 9 Eucalyptus gomphocephala trees, and 9Eucalyptus cladocalyx trees for a total of 28 trees. The objective of the study reported here was to investigate the within-tree and between species variability of selected physical and processing properties determining the suitability of these three species for lumber production. The density, microfibril angle, spiral grain angle, MOE, MOR, radial and tangential shrinkage, twist, bow, splitting, and collapse were measured in a radial and longitudinal gradient. Valuable insights were gained which could provide decision support for planting, processing and further research on these species when grown in arid conditions. The E. grandis × camaldulensis hybrid was inferior in terms of most relevant properties to the other two species evaluated. The main shortcoming of both E. gomphocephala and E. cladocalyx was the high levels of twist in lumber.

  • 44.
    Wimmer, Rupert
    et al.
    Univ Bodenkultur Wien BOKU.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Effects of Reaction Wood on the Performance of Wood and Wood-Based Products2014In: The Biology of Reaction Wood / [ed] Gardiner, B., Barnett, J., Saranpää, P., Gril, J., Springer, 2014, 1, p. 225-248Chapter in book (Refereed)
    Abstract [en]

    Compression wood in softwoods and tension wood in hardwoods have properties, which adversely affect its usefulness for wood products. This chapter shows that reaction wood can be associated with many unsuitable wood properties. The results vary due to the fact that definitions about occurrence and severity of reaction wood are scarcely documented. A few properties seem to be even benefitting from the presence of reaction wood: the higher smoothness of compression wood surfaces, better shear strength of compression wood, higher toughness and impact resistance when tension wood is present, lower water uptake and swelling in fibreboards containing compression wood, and higher durability against fungi of compression wood. However, these are outweighed by disadvantages, which is the reason why reaction wood has a bad reputation in industry. The problem with reaction wood is that it is in most cases mixed with normal wood, which leads to non-uniform and more variable properties. This may lead to non-uniform swelling and shrinking, causing distortions, with additional problems of reduced strength and unfavourable surface properties. Wood-based materials such as particle boards or fibreboards are generally less prone to problems associated with reaction wood than solid wood products. With knowledge-based production methods the utilization of different wood types, including reaction wood, might be feasible.

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