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  • 1.
    Blyberg, Louise
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Olsson, Anders
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Källsner, Bo
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Fire exposed light-frame timber walls: A study on the effect of geometrical reduction of a vertically loaded I-section stud2009Rapport (Övrigt vetenskapligt)
    Abstract [en]

    A wooden I-stud as a member of a light-frame timber wall is modelled with reducing flange width to simulate fire exposure. The stud is loaded with a vertical load and the effect of restraints from one gypsum board and the top and bottom rail is considered. Geometry and material values are chosen to correspond to a stud with flanges of solid wood and web of OSB (oriented strand board).

    A model with shell and beam elements is implemented in Abaqus. A buckling analysis is performed on a perfectly straight stud and then a geometrically nonlinear analysis is performed on a stud with an initial curvature. Both the buckling analysis and the geometrically nonlinear analysis show that even a large reduction of the flange width results only in moderate changes of the load-carrying capacity of the structure.

    In the report diagrams are presented from the geometrically nonlinear analysis where the critical load is easy to read once a failure stress is determined, but an estimate of the the failure stress is not given here.

  • 2.
    Briggert, Andreas
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Hu, Min
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Evaluation of three dimensional fibre orientation in Norway spruce using a laboratory laser scanner2016Ingår i: WCTE 2016: World Conference on Timber Engineering, Vienna: Vienna University of Technology , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper addresses laser scanning and utilization of the tracheid effect for determination of local fibre orientation, which is decisive for strength and stiffness of timber. A newly developed laboratory laser scanner that can be used for high resolution and high precision scanning of wood surfaces is used for in-depth assessment of a single Norway spruce specimen that contains a knot. It is assumed that the specimen has a plane of symmetry, through the knot, and by splitting the specimen in two parts it is possible to determine fibre orientation on orthogonal planes. Hence, by relying on the assumption of symmetry, the fibre orientation in 3D space can also be determined. The results are used to evaluate the possibility of utilizing the tracheid effect for determination of the out-of-plane fibre angle of an investigated surface. Furthermore, the results are used for verification of a theoretical fibre orientation model that has often been used by researchers.

  • 3.
    Briggert, Andreas
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Hu, Min
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Tracheid effect scanning and evaluation of in-plane and out-of-plane fibre direction in Norway spruce using2018Ingår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 50, nr 4, s. 411-429Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Local fiber direction is decisive for both strength and stiffness in timber. In-plane fiber direction on surfaces of timber can be determined using the so-called tracheid effect which is frequently used in both research and industry applications. However, a similar established method does not exist for measuring the out-of-plane angle, also known as diving angle. The purposes of this article were to evaluate if the tracheid effect can also be used to determine, with reasonable accuracy, the out-of-plane angle in Norway spruce and to verify an existing mathematical model used to calculate the fiber direction in the vicinity of knots. A newly developed laboratory laser scanner was applied for assessment of fiber directions in a single Norway spruce specimen containing a knot. It was assumed that the specimen had a plane of symmetry through the center of the knot, and by splitting the specimen through this plane into two parts, it was possible to make measurements on orthogonal planes. The results showed that the out-of-plane angle could not be determined with very high accuracy and the difficulties related to this objective were analyzed. Regarding the mathematical model of fiber direction in the vicinity of a knot, fiber directions calculated on the basis of this model agreed well with experimentally obtained fiber directions, but successful application of the model requires that the geometry of the knot is known in detail.

  • 4.
    Briggert, Andreas
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Modelling 3D orientation of knots in timber on the basis of dot laser scanning and the tracheid effect2015Ingår i: / [ed] Josef Eberhardsteiner and Michael Kaliske, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ongoing research concerns the possibility of determining the 3D orientation of wood fibres within the entire volume of a wooden board using surface information from laser scanning. Previous research, Olsson and Oscarsson [1], has shown that the fibre orientation of side boards can be determined on the basis of such information. The present research is extended to also comprise boards cut from the centre of the log and a first step in this work is to establish 3D models of knots in boards on the basis of information from dot laser scanning of surfaces.

    In comparison with other approaches aiming at 3D models of knots and wood fibre orientation, e.g. Guindos and Guaita[2] and Hackspiel et al. [3], the present model relies to a larger extent on the actual fibre orientation measured on each individual board, rather than on general assumption and mathematical models of typical fibre orientation alone.  

    The fact that all data needed for the model can be sampled in sawmill production speed means that developed models could be used as a basis for advanced strength grading methods, for grading with respect to shape stability and for other purposes of industrial interest.

  • 5.
    Briggert, Andreas
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Three dimensional knot models based on surface laser scanning2015Ingår i: Proceedings 19th International Nondestructive Testing and Evaluation of Wood Symposium Rio de Janeiro, Brazil, 23-25 September, 2015. / [ed] Ross, Robert J.; Gonçalves, Raquel; Wang, Xiping,, Madison, USA: USDA, Forest Service, Forest Products Laboratory , 2015, Vol. 19, s. 83-90Konferensbidrag (Refereegranskat)
    Abstract [en]

    Most machine strength grading methods of today result in limited grading accuracy and poor yield in higher strength classes. A new and more accurate grading method utilizing laser scanning technique to determine the in-plane fibre directions on board surfaces was recently approved for the European market. In this, however, no consideration is taken to the out-of-plane direction of the fibres. A first step towards scanning-based 3D models of the fibre orientation is the establishment of 3D knot models. In this investigation laser scanning was used to identify knot surfaces on longitudinal board surfaces. By means of developed algorithms knot surfaces that belonged to the same physical knot visible on different sides of the board were identified. All knots with surface areas larger than 100 mm2 were correctly identified and modeled in 3D. This is a promising starting point for further development of the new grading method based on laser scanning.

  • 6.
    Briggert, Andreas
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Three-dimensional modelling of knots and pith location in Norway spruce boards using tracheid-effect scanning2016Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 74, nr 5, s. 725-739Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Knots and the orientation of fibres in timber are decisive for the stiffness and strength of boards. Due to large property variations between members, strength grading is necessary. High resolution information of the orientation of fibres, both on surfaces and within members, would enable development of more accurate grading methods than those available today. A step towards three-dimensional (3D) models of the fibre orientation of the entire board volume is the establishment of 3D knot models based on scanning. The light from a dot laser illuminating the surface of a softwood board will, due to the tracheid effect, spread more along the fibres than across resulting in the dot entering an elliptical shape. In this investigation both the shape of the ellipse and the direction of its major axis were used to estimate the 3D fibre orientation on board surfaces. Knot surfaces were identified where the angle between the estimated 3D fibre direction and an approximated direction of the board’s pith exceeded a threshold value. By means of algorithms based on polar coordinates, knot surfaces which belonged to the same physical knot visible on different sides of the board were identified and as a result the position, orientation and volume of each knot were determined. Based on this information, a more accurate position of the board’s pith along the board was calculated. The established models showed good agreement with physical boards. The models constitute a promising starting point for further development of strength grading methods based on tracheid-effect scanning.

  • 7.
    Gečys, Tomas
    et al.
    Vilnius Gediminas Technical University, Lithuania.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Kajėnasa, Simonas
    Vilnius Gediminas Technical University, Lithuania.
    Influence of the rope effect on the slip curve of laterally loaded, nailed and screwed timber-to-timber connections2019Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 228, artikel-id 116702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Timber-to-timber connections with different types of screws and nails were experimentally investigated with the aim to quantify the contribution of their axial resistance to their slip and their lateral load bearing capacity, which is the so-called rope effect in dowel-type timber connections. Five different types of screws, including partly threaded and double-threaded screws, as well as three types of nails, including smooth round nails, twisted square-sectioned and grooved nails, were used in the experimental investigations in order to cover a broad range of axial resistance of fasteners. Their behavior was tested in single shear and double shear timber-to-timber connections. In addition to connection testing, system and material properties were experimentally determined. This gave input to design equations and allowed for a comparison of the mechanical model in the European design standard for timber structures, Eurocode 5, with experiments. Experiments indicate that the initial slip modulus in the quasi-elastic domain is not influenced by withdrawal capacity of the fastener, while it shows pronounced influence on load-carrying capacity and the nonlinear shape of the slip curve of the connection at larger deformations. Rope effect strongly depends on fastener properties. High axial resistance of fasteners leads to highly non-linear slip curves and design equations tended to underestimate strength including the rope effect up to a displacement limit of 15 mm. Experimentally observed failure modes were well in line with the theoretical failure modes predicted by the design model. The provided experimental results are motivation for improvement of design models and development of analytical and numerical models that account for nonlinear effects in the complex load transfer mechanism.

  • 8.
    Habite, Tadios
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Automatic detection of pith location along boards of Norway spruce on the basis of data from optical scanning of longitudinal surfaces2019Ingår i: 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, s. 64-64Konferensbidrag (Refereegranskat)
    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.

  • 9.
    Habite, Tadios
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Detection of Pith Location of Norway Spruce Timber Boards on the Basis of Optical Scanning2019Ingår i: 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, s. 268-275Konferensbidrag (Refereegranskat)
    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.

  • 10.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Briggert, Andreas
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Säll, Harald
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Growth layer and fibre orientation around knots in Norway spruce: a laboratory investigation2018Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 52, nr 1, s. 7-27Artikel i tidskrift (Refereegranskat)
    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.

  • 11.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Briggert, Andreas
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Säll, Harald
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Three dimensional growth layer geometry and fibre orientation around knots: a laboratory investigation2016Ingår i: Proceedings of WCTE 2016 World Conference on Timber Engineering / [ed] Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Vienna: Vienna University of Technology , 2016Konferensbidrag (Refereegranskat)
  • 12.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Johansson, Marie
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Olsson, Anders
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Bengtsson, Charlotte
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Grading of sawn timber using the vibration technique: locating imperfections based on flexural mode shapes2011Ingår i: 17th international nondestructive testing and evaluation of wood symposium / [ed] Ference Divos, Sopron, Hungary: University of West Hungary , 2011, s. 269-276Konferensbidrag (Refereegranskat)
    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.

  • 13.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Comparison of local variation of modulus of elasticity determined on basis of scanned fiber angles and full strain field measurements2013Ingår i: The 18th International Nondestructive Testing and Evaluation of Wood Symposium, Madison, WI, USA, 2013Konferensbidrag (Refereegranskat)
    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.

  • 14.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    SP Tech Res Inst Sweden, SP Wood Technol, Växjö.
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Local variation of modulus of elasticity in timber determined on the basis of non-contact deformation  measurement and scanned fibre orientation2015Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, nr 1, s. 17-27Artikel i tidskrift (Refereegranskat)
    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.

  • 15.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Local bending stiffness for prediction of bending strength: Evaluation of models and conceptManuskript (preprint) (Övrigt vetenskapligt)
  • 16.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    An Application of 3D Fiber Angles Identified through Laser Scanning Based on Tracheid Effect2015Konferensbidrag (Refereegranskat)
  • 17.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Modelling local bending stiffness based on fibre orientation in sawn timber2018Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, nr 6, s. 1605-1621Artikel i tidskrift (Refereegranskat)
    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.

  • 18.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Serrano, Erik
    Lund University.
    Assessment of a Three-Dimensional Fiber Orientation Model for Timber2016Ingår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 48, nr 4, s. 271-290Artikel i tidskrift (Refereegranskat)
    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.

  • 19.
    Jarnerö, Kirsi
    et al.
    SP Wood Technology, SP Technical Research Institute of Sweden.
    Bolmsvik, Åsa
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Olsson, Anders
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Effect of flexible supports on vibration performance of timber floors2012Ingår i: Euronoise, Prague 2012, 10-13 June, 2012: Proceedings, European Acoustics Association (EAA), 2012, s. 214-219Konferensbidrag (Refereegranskat)
    Abstract [en]

    In residential multi-storey buildings of timber it is of great impor-tance to reduce the flanking transmission of noise. Some buildingsystemsdothisbyinstallingavibration-dampingelasticinterlayer,Sylomerror Sylodynr, in the junction between the support andthefloorstructure.Thisinterlayeralsoimprovesthefloorvibrationperformance by adding damping to the structure. In the presentwork the vibration performance of a floor with such interlayershas been investigated both in laboratory and field tests. A pre-fabricated timber floor element was tested in laboratory on rigidsupports and on supports with four different types of interlayers.Theresultsarecomparedwithin situtests on a copy of the samefloorelement.Theeffectonvibrationperformancei.e.frequencies,damping ratio and mode shapes is studied. A comparison of theinsitutestandthetestwithelasticinterlayerinlaboratoryshowsthatthe dampingin situis approximately three times higher than on asingle floor element in the lab. This indicates that the dampinginsituisaffectedbethesurroundingbuildingstructure.Theachieveddamping ratio ishighly dependent onthe mode shapes. Mode sha-pes that have high mode shape coefficients along the edges wherethe interlayer material is located, result in higher modal dampingratios. The impulse velocity response, that is used to evaluatethe vibration performance and rate experienced annoyance in thedesign of wooden joist floors, seems to be reduced when adding elastic layers at the supports.

  • 20.
    Jarnerö, Kirsi
    et al.
    SP Technical research institute of Sweden.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Olsson, Anders
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    In situ testing of timber floor vibration properties2010Ingår i: Proceedings of the 11th World Conference on Timber Engineering / [ed] Ario Ceccotti, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the present work the change in natural frequencies, damping and mode shapes of a prefabricated timber floor element have been investigated when it was integrated into a building structure. The timber floor element was first subjected to modal testing in laboratory with ungrounded and simply supported boundary conditions, and then in situ at different stages of building construction. The first five natural frequencies, damping ratios and mode shapes of the floor element and the entire floor were extracted and analysed. It may be concluded that the major change in natural frequencies 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 largely are constrained in their movement. The

    in situ conditions have a great influence on the damping, which probably depends on the damping characteristics of the supports, but also on the fact that the floor is integrated into the building and interacts with it. There is a slight increase of damping in the floor over the different construction stages and the damping values seem to decrease with ascending mode order. The relative change also seems to decrease with increasing number of storeys built.

  • 21.
    Jarnerö, Kirsi
    et al.
    Technical Research Institute of Sweden, SP Trätek, Växjö, Sweden.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Olsson, Anders
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Vibration properties of a timber floor assessed in laboratory and during building construction2010Ingår i: Proceedings of INTER-NOISE: the 39th International Congress and Exposition on Noise Control Engineering, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the present work the change in natural frequencies, damping and mode shapes of a prefabricated timber floor element have been investigated when it was integrated into a building structure. The timber floor element was first subjected to modal testing in laboratory with ungrounded and simply supported boundary conditions, and then in situ at different stages of building construction. The first five natural frequencies, damping ratios and mode shapes of the floor element and the entire floor were extracted and analysed. It may be concluded that the major change in natural frequencies 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 largely are constrained in their movement. The in situ conditions have a great influence on the damping, which depends on the damping characteristics of the supports, but also on the fact that the floor is integrated into the building and interacts with it. There is a slight increase of damping in the floor over the different construction stages and the damping values seem to decrease with ascending mode order.

  • 22.
    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
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Vibration properties of a timber floor assessed in laboratory and during construction2015Ingår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 82, s. 44-54Artikel i tidskrift (Refereegranskat)
    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.

  • 23.
    Jarnerö, Kirsi
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Simmons, C
    Bard, V
    Vibration performance of lightweight floors in multifamily houses: Resident survey and field measurementManuskript (preprint) (Övrigt vetenskapligt)
  • 24.
    Johansson, Marie
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Mahapatra, Krushna
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Vessby, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Blom, Åsa
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Expert competence for sustainable timber engineering: a master program in close cooperation between industry and academia2014Ingår i: WCTE 2014 - World Conference on Timber Engineering, Proceedings, 2014Konferensbidrag (Refereegranskat)
    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.

  • 25.
    Johansson, Marie
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Olsson, Anders
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Grading of sawn timber with dynamic methods – influence of defect2010Ingår i: WCTE 2010 – The 11th World Conference on Timber Engineering, Riva del Garda, Italy, 20-24 June, 2010Konferensbidrag (Refereegranskat)
  • 26.
    Johansson, Marie
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Olsson, Anders
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Grading of sawn timber with dynamic methods – influence of defects2009Ingår i: Proceedings of the COST E53 Workshop, Lisbon 22-23 October 2009 / [ed] José António Santos, 2009Konferensbidrag (Övrigt vetenskapligt)
  • 27.
    Lukacevic, Markus
    et al.
    Vienna University of Technology, Austria.
    Kandler, Georg
    Vienna University of Technology, Austria;Dynardo Austria GmbH, Austria.
    Hu, Min
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Füssl, Josef
    Vienna University of Technology, Austria.
    A 3D model for knots and related fiber deviations in sawn timber for prediction of mechanical properties of boards2019Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 166, s. 1-18, artikel-id 107617Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Increased use of wood has led to complex timber constructions and new types of engineered wood products. In simulations, however, mainly simplified models are used to describe this material with its strongly varying properties. Therefore, reliable prediction tools for mechanical properties of wooden boards are needed. Those varying properties mainly originate from knots and fiber deviations. Thus, we use fiber directions on board surfaces to reconstruct knots within boards. Combined with a fiber deviation model we assess our model with experiments on different levels: fiber directions on surfaces, strain fields and bending stiffness profiles.

    This model now better describes fiber patterns near knots and knot clusters. Also, we showed that accurate modeling of the pith is important to avoid large regions of incorrect fiber deviations. Furthermore, modified knot stiffness properties were successfully used to consider pre-cracked knots. Finally, we obtained multiple bending stiffness profiles, where we showed that even local effects can be simulated accurately.

    We anticipate our tool to be a starting point for improving strength grading models, where effects of knot configurations can be studied more easily than with experiments alone. Furthermore, the presented improvements will render the simulation of realistic failure mechanisms in wooden boards more likely.

  • 28.
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Determination of sawn timber properties using laser scanning: Development potentials and industrial applications2016Ingår i: WCTE 2016 - World Conference on Timber Engineering: August 22-25, 2016, Vienna, Austria. e-book, Full Papers / [ed] Josef Eberhardsteiner, Wolfgang Winter, Alireza Fadai, Martina Pöll, Vienna: tuverlag , 2016, s. 82-91Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper starts with an overview of methods for machine strength grading of timber being used in industry. It discusses attempts that have been made over the years to improve the accuracy of different grading concepts. Then a newly approved method based on laser scanning and utilization of the tracheid effect is presented. It utilizes high resolution data supplied by an industrial scanner and it gives, in comparison to other methods, very accurate results. Still it is based on several crude assumptions. Therefore the latter part of the paper takes a starting point in the limitations of this scanning based method and discusses what can be done within research and development to reach an even higher grading accuracy. Future work should lead to detailed and accurate models for timber, including geometry of knots, growth layers and fibre orientation in 3D and information of local material stiffness properties, and it should be possible to establish such models for individual boards in productions speed. Some recent and ongoing research that contributes in this direction is discussed. With access to accurate timber models several different strategies for prediction of strength and other engineering properties would be possible.

  • 29.
    Olsson, Anders
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Probabilistic Analysis and Optimization of Roof Trusses2010Ingår i: Electronic Journal of Structural Engineering, ISSN 1443-9255, E-ISSN 1443-9255, Vol. 10, s. 74-89Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of gap between wooden members and displaced nail-plates in roof trusses is investigated by means of probabilistic calculations and structural optimization. The employed mechanical model, using the finite element method, captures the non-linear behaviour of the nail-plate joints. The joint stiffness involves the size and location of the nail-plate, and the presence of contact or gap respectively between the wooden members. The analysis shows that even small initial gaps considerably increase the deflection of a roof truss. Misplaced nail-plates also effect the deflection negatively, but it is also shown that the deflection can be significantly decreased, and the utilization of nail-plates improved, by optimizing the nail-plate positions with respect to critical load cases and requirements.

  • 30.
    Olsson, Anders
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Byggteknik.
    Bolmsvik, Åsa
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Byggteknik.
    Acoustics in Wooden Buildings - State of the Art 20082008Ingår i: Joint Baltic-Nordic Acoustics Meeting 2008: BNAM2008-2, Acoustical Society of Iceland, Reykjavik , 2008, s. 4-Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Acoustics is an important performance characteristic for building with wood and a prerequisite for the acceptance of wooden buildings by building industry, building owners and consumers. However, the research in this area has been limited in Sweden during recent years.

    Therefore, a national consortium was initiated by SP Trätek in 2007 in order to utilize available resources more efficiently and to maintain and develop the competence in the field of Acoustics in wooden buildings. The consortium consists of all national R&D performers, leading industry companies within the building, building materials and wood sectors and leading consultants.

    The aim is to present the state of the art, define industrial needs for producing wooden buildings with high acoustic performance and to define further research needs to reach that goal.

    A state of the art report is the first result from the new Swedish consortium. The report includes a literature survey, analysis and identification of industrial needs for producing wooden buildings with good acoustic comfort and further research needs to reach that goal.

    The aim is also to further develop contacts and cooperation with international actors.

  • 31.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Briggert, Andreas
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Increased yield of finger jointed structural timber by accounting for grain orientation utilizing the tracheid effect2019Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736XArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    Finger joints in structural timber and glulam lamellae are often used to enable production of long members or to allow forre-connection of parts of a member after removal of weak sections. According to the European Standard EN 15497, certainmargins are required between knots and a finger joint in structural timber, which means that a considerable amount of clearwood becomes waste when finger joints are applied. The purpose of this paper was to investigate the possibility of reducingthe quantity of waste using different criteria for placement of finger joints. The investigation was based on (1) applicationof methods of colour scanning and tracheid effect scanning to detect knots and grain disturbance on board surfaces, and (2)interpretation of the requirements of EN 15497 regarding where finger joints may be placed. The standard’s requirementwhen producing finger joints is that the minimum distance between a knot and a finger joint is three times the knot diameter.The standard allows for the minimum distance between a knot and a finger joint to be shortened to 1.5 times the diameterwhen the local fibre orientation is measured. Utilizing this in simulated production resulted in reduction of waste from 7.4to 4.0%, when using finger joints simply to produce timber of long lengths. If finger joints are also used to re-connect partsof members after removal of weak sections, even larger savings can be made. Furthermore, it is concluded that knowledgeof fibre orientation obtained from scanning could be used not only to decrease the waste in production but also to increasethe quality of finger joints.

  • 32.
    Olsson, Anders
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Byggteknik.
    Jarnerö, Kirsi
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Byggteknik.
    Källsner, Bo
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Byggteknik.
    Wooden floor structures with high transverse stiffness2008Ingår i: 10th World Conference on Timber Engineering, 2008Konferensbidrag (Refereegranskat)
  • 33.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Källsner, Bo
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Evaluation of shear modulus of structural timber utilizing dynamic excitation and FE analysis2012Ingår i: Proceedings of CIB -W18, 2012Konferensbidrag (Refereegranskat)
  • 34.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Källsner, Bo
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Shear modulus of structural timber evaluated by means of dynamic excitation and FE analysis2015Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 48, nr 4, s. 977-985Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study the results from dynamic excitation of 105 centre boards of Norway spruce in edgewise bending are evaluated with respect to shear modulus using the FE method. Advantages of the method presented here, in relation to the torsion method given in EN 408 (Timber structures—structural timber and glued laminated timber—determination of some physical and mechanical properties, 2010), are that the testing is very simple to carry out and also that the shear stresses occur in the same way as in a beam subjected to bending. Although no alternative methods for evaluation of the shear modulus were applied in this study, results indicating a robustness of the suggested method are presented. According to calculations the estimated shear modulus varies considerably between different boards. The calculated mean value and standard deviation of the dynamic shear modulus is about 744 and 106 MPa, respectively. No significant correlation between the estimated shear modulus and the measured static modulus of elasticity in bending was found, but a correlation between calculated shear modulus and density was identified (R2 = 0.24). Conclusions of the results are that dynamic excitation of boards should be considered as an alternative method for determination of shear modulus in EN 408 (Timber structures—structural timber and glued laminated timber—determination of some physical and mechanical properties, 2010), and a relation between the board density and the board shear modulus, rather than a relation between the board MOE and the board shear modulus, should be stated in EN 338 (Structural timber—strength classes, 2009).

  • 35.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Källsner, Bo
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Oscarsson, Jan
    SP Sveriges Tekniska Forskningsinstitut.
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Nytt paradigm för hållfasthetssortering av konstruktionsvirke: Projektrapport ett2013Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Den undersökning som redovisas i denna rapport har genomförts under hösten 2012 och våren 2013 inom projektet "Nytt paradigm för hållfasthetssortering av konstruktionsvirke". Projektet som kommer att pågå under perioden december 2011 till juni 2014 går ut på att för industriellt bruk utveckla en nyligen föreslagen metod för hållfasthetssortering av konstruktionsvirke, vilken baseras på laserskanning i kombination med dynamisk excitering och densitetsbestämning av virke. Projektet finansieras till 50 % av VINNOVA och till 50 % av de företag som medverkar i projektet, nämligen Innovativ Vision AB (IV), Vida Vislanda AB, Södra Timber AB, Derome Timber AB och Dynalyse AB. Linnéuniversitetet (Lnu) och SP Sveriges Tekniska Forskningsinstitut AB (SP) samverkar med nämnda företag i utförandet av forskningen.

    Syftet med undersökningen är i först hand att utvärdera alternativa sätt för att bestämma densitet för virke och att verifiera implementeringen av programvara för industriellt bruk. Syftet är också att ta fram ett utökat material för att bedöma vilken precision den nya sorteringsmetoden kan erbjuda och för att bedöma hur känslig den är för olika typer förändringar och störningar som kan uppkomma. Undersökningen bygger på ett begränsat material och en mer omfattande undersökning planeras för genomförande under senare delar av projektet.

  • 36.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Källsner, Bo
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY). SP Sveriges Tekniska Forskningsinstitut.
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Nytt paradigm för hållfasthetssortering av konstruktionsvirke: Projektrapport två2014Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Undersökningen som redovisas i denna rapport har genomförts under hösten 2013 och våren 2014 inom projektet "Nytt paradigm för hållfasthetssortering av konstruktionsvirke". Projektet, som pågår under perioden december 2011 till juni 2014, går ut på att för industriellt bruk utveckla en nyligen föreslagen metod för hållfasthetssortering av konstruktionsvirke, vilken baseras på laserskanning i kombination med dynamisk excitering och densitetsbestämning av virke. Projektet finansieras till 50 % av VINNOVA och till 50 % av de företag som medverkar i projektet, nämligen Innovativ Vision AB (IV), Vida Vislanda AB, Södra Timber AB, Derome Timber AB och Dynalyse AB. Linnéuniversitetet (Lnu) och SP Sveriges Tekniska Forskningsinstitut AB (SP) samverkar med nämnda företag i utförandet av forskningen.

    Ett syfte med undersökningen är att på ett stort material bestående av många olika virkesdimensioner verifiera de starka statistiska samband som sedan tidigare påvisats för ett begränsat antal plankor och dimensioner, mellan å ena sidan indikerande egenskaper som baseras på mätningar och beräkningar och å andra sidan böjstyrka, elasticitetsmodul och densitet. Ett annat syfte med undersökningen är att visa att nödvändig data kan samlas in av samma utrustning och under samma förhållanden som kommer att gälla vid framtida hållfasthetssortering baserad på den aktuella metoden. Slutligen är ett syfte att samla in och dokumentera data som kan användas för forskning och utveckling både inom och efter det att det aktuella projektet har avslutats.

  • 37.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Strength grading based on high resolution laser scanning: performance of a procedure newly approved for the European market2015Ingår i: Proceedings of the 19th International Nondestructive Testing and Evaluation of Wood Symposium / [ed] Ross, Robert J.; Goncalves, Raquel; Wang, Xiping, Madison, USA: USDA, United States Department of Agriculture, Forest Service, Forest Products Laboratory , 2015, Vol. 19, s. 232-240Konferensbidrag (Refereegranskat)
    Abstract [en]

    Strength grading of timber is necessary to ensure sufficient structural performance of the material, and machines based on different types of non-destructive measurements are available on the market. The purpose of this paper is to present results on an investigation of a new method and procedure for machine strength grading that is based on laser scanning and utilization of the tracheid effect, in combination with dynamic excitation and weighing. The investigated sample comprised more than 900 pieces of timber of Norway spruce (Picea abies) from Sweden, Norway and Finland. The coefficient of determination between the indicating property (IP) to bending strength and the measured bending strength was as high as R2 = 0.69, while the coefficient of determination between dynamic MOE and measured bending strength was R2 = 0.53. A comparison of the performance with what have been presented for machines that are based on X-ray in combination with dynamic excitation indicates that the new method/procedure will surpass such machines. 

  • 38.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Strength grading on the basis of high resolution laser scanning and dynamic excitation: a full scale investigation of performance2017Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 75, nr 1, s. 17-31Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effective utilization of structural timber requires grading and indicating properties (IPs) that are able to predict strength with high accuracy, and machines that are able to measure the underlying board properties at a speed that corresponds to the production speed of sawmills. The aim of this research is to assess the performance of a new machine strength grading method/procedure which was recently approved for the European market and to compare the performance of it with the performance of other available techniques. The novel method is based on laser scanning utilizing the tracheid effect, in combination with data from dynamic excitation and weighing. Applied indicating properties are defined in detail and results presented include assessment of the repeatability, coefficients of determination between IPs and grade determining properties, and examples of the yield achieved in different strength classes and combinations of strength classes. The investigated sample comprised more than 900 pieces of timber of Norway spruce (Picea abies) from Sweden, Norway and Finland. For this sample the coefficient of determination between the IP to bending strength and the measured bending strength was as high as R2 = 0.69, while the coefficient of determination between dynamic modulus of elasticity (MOE) and measured bending strength was R2 = 0.53. The yield in high strength classes, C35 and above, become about twice as high using the new method/procedure compared to machines using dynamic MOE as IP. A comparison of the performance with what have been presented for machines that are based on X-ray in combination with dynamic excitation indicates that the new method/procedure will surpass such machines as well. 

  • 39.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    SP Technical Research Institute of Sweden, Sweden.
    Three dimensional fibre orientation models for wood based on laser scanning utilizing the tracheid effect2014Ingår i: Proceedings of the 2014 World Conference on Timber Engineering (WCTE), Quebec City, Canada, August 10−14, 2014, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recentresearch has shown that machine strength grading based on tracheid effectscanning of fibre directions projected on board surfaces can provide moreaccurate strength predictions than today’s grading methods. Scanning techniquesin which 3D fibre orientations can be taken into account would most likelyimprove the strength grading results even further. In this investigation thepossibility of determining such 3D orientations by dot laser scanning wasinvestigated. For a set of 20 side boards, scanning data was used to calculatetraversing knot directions which were in turn applied to determine pithlocation and root end of original logs. By means of the shape of laser dots,which due to the tracheid effect are turned elliptic on board surfaces, and thedetermined pith location, the size and direction of the diving angle of thefibres was calculated. The research showed that this angle can be accuratelydetermined in the vicinity of knots.

  • 40.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Oscarsson, Jan
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Johansson, Marie
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Källsner, Bo
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Dynamic excitation and higher bending modes for prediction oftimber bending strength2010Ingår i: Proceedings of the final conference of COST action E53, 2010Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 41.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Oscarsson, Jan
    SP Technical Research Institute of Sweden, Videum Science Park, 351 96, Växjö, Sweden.
    Johansson, Marie
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Källsner, Bo
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Prediction of timber bending strength on basis of bending stiffness and material homogeneity assessed from dynamic excitation2012Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 46, nr 4, s. 667-683Artikel i tidskrift (Refereegranskat)
    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.

  • 42.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Oscarsson, Jan
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Johansson, Marie
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Källsner, Bo
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Prediction of timber bending strength using dynamic excitation of bending modes2010Ingår i: Proceedings of the 11th World Conference on Timber Engineering / [ed] Ario Ceccotti, 2010Konferensbidrag (Refereegranskat)
    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.

  • 43.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE). SP Technical Research Institute of Sweden.
    Serrano, Erik
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Källsner, Bo
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Prediction of timber bending strength and in-member cross-sectional stiffness vartiation on basis of local wood fibre orientation2013Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 71, nr 3, s. 319-333Artikel i tidskrift (Refereegranskat)
    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.

  • 44.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Pot, Guillaume
    LaBoMaP, France.
    Viguier, Joffrey
    LaBoMaP, France.
    Faydi, Younes
    LaBoMaP, France.
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Performance of strength grading methods based on fibre orientation and axial resonance frequency applied to Norway spruce (Picea abies L.), Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and European oak (Quercus petraea (Matt.) Liebl./Quercus robur L.)2018Ingår i: Annals of Forest Science, ISSN 1286-4560, E-ISSN 1297-966X, Vol. 75, nr 4, artikel-id 102Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Key messageMachine strength grading of sawn timber is an important value adding process for the sawmilling industry. By utilizing data of local fibre orientation on timber surfaces, obtained from laser scanning, more accurate prediction of bending strength can be obtained compared to if only axial vibratory measurements are performed. However, the degree of improvement depends on wood species and on board dimensions. It is shown that a model based on a combination of fibre orientation scanning and axial vibratory measurement is very effective for Norway spruce (Picea abiesL.) and Douglas fir (Pseudotsuga menziesii(Mirb.) Franco). For European oak (Quercus petraea(Matt.) Liebl./Quercus roburL.) boards of narrow dimensions, axial vibratory measurements are ineffective whereas satisfactory results are achieved using a model based on fibre orientation.ContextMachine strength grading of sawn timber is an important value adding process for the sawmilling industry.AimsThe purpose of this paper has been to compare the accuracy of several indicating properties (IPs) to bending strength when applied to Norway spruce (Picea abies L.), Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and European oak (Quercus petraea (Matt.) Liebl./Quercus robur L.).MethodsThe IPs were determined for a set of data comprising scanned high-resolution information of fibre orientation on board surfaces, axial resonance frequency, mass and board dimensions.ResultsWhereas dynamic axial modulus of elasticity (MoE) gave good prediction of bending strength of Norway spruce (R-2=0.58) and Douglas fir (R-2=0.47), it did not for narrow dimension boards of oak (R-2=0.22). An IP based on fibre orientation gave, however, good prediction of bending strength for all three species and an IP considering both dynamic axial MoE and local fibre orientation for prediction of bending strength gave very good accuracy for all species (Norway spruce R-2=0.72, Douglas fir R-2=0.62, oak R-2=0.59). Comparisons of results also showed that scanning of fibre orientation on all four sides of boards resulted in more accurate grading compared to when only the two wide faces were scanned.ConclusionData of local fibre orientation on wood surfaces give basis for accurate machine strength grading. For structural size timber of Norway spruce and Douglas fir, excellent grading accuracy was achieved combining such data with data from vibratory measurements. The improvements achieved enable substantial increase of yield in high-strength classes.

  • 45.
    Olsson, Anders
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Serrano, Erik
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Källsner, Bo
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Förfarande och anordning för utvärdering av en bräda av trä2014Patent (Övrig (populärvetenskap, debatt, mm))
    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.

  • 46.
    Oscarsson, Jan
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Determination of tensile strain fields in narrow Norway spruce side boards as a basis for verification of new machine strength grading methodsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Today’s methods for machine strength grading of structural timber result, in general, in strength predictions with a rather low accuracy. A need for development of more precise methods has been identified. Application of stiffness in terms of locally determined MOE as indicating property is an evident starting point for such a process. Development of new grading procedures and models require laboratory verification, and this research investigates the possibility of using contact-free deformation measurement technique based on white-light digital image correlation (DIC) for this purpose. A sample of nine Norway spruce (Picea abies) side boards of narrow dimensions was tested in tension according to the European Standard EN 408. Simultaneously, deformations along the entire length of one of the flatwise surfaces of each board were measured using two master-slave connected DIC systems. Strain fields were subsequently calculated. To evaluate the accuracy of the measurement technique, local MOE determined traditionally, i.e. on the basis of elongations measured in accordance with EN 408, was compared with corresponding MOE values calculated on the basis of DIC deformation measurements. Acceptable agreement between compared MOEs were achieved and the accuracy of MOE values determined on the basis of the DIC technique was on the same level as requirements laid down in EN 408. However, the resolution of the information supplied by the DIC technique can, in contrast to elongations measured traditionally, be used to gain detailed knowledge regarding local MOE in evaluated boards. Therefore, based upon achieved results, in combination with certain identified potentials for measurement improvements, it is concluded that DIC technique can be used as a tool for development and laboratory verification of new strength grading methods.

  • 47.
    Oscarsson, Jan
    et al.
    SP Technical Research, Institute of Sweden, Växjö.
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Improving Strength of Glulam Laminations of Norway Spruce Side Boards by Removal of Weak Sections Using Optimized Finger Jointing2014Ingår i: Materials and Joints in Timber Structures: Recent Developments of Technology / [ed] Simon Aicher; H.-W. Reinhardt ;Harald Garrecht, Springer, 2014, s. 801-811Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recent research has shown that glulam laminations of Norway spruce side boards possess excellent structural properties. This investigation concerns the possibility of improving the performance of such laminations through elimination of weak board sections by means of finger jointing. Sections to be removed were identified using profiles of edgewise bending stiffness determined on the basis of scanned fibre angle fields on board surfaces. The difference in average tension strength and average tension stiffness, respectively, between a group of finger jointed boards and a reference group of non-jointed boards was evaluated. Joints were inserted in the first group with an average distance of 2.4 m. It was found that the finger jointing gave a considerable increase of strength (36 %), whereas the stiffness improvement was not as evident. Based upon the results, it can be assumed that application of finger jointed side board laminations will result in glulam beams with very high strength.

  • 48.
    Oscarsson, Jan
    et al.
    SP Technical Research Institute of Sweden, Sweden.
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Localized modulus of elasticity in timber and its significance for the accuracy of machine strength grading2014Ingår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 46, nr 4, s. 489-501Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    From previous research, it is well known that a localized modulus of elasticity (MOE) is a better indicating property (IP) of strength than an MOE averaged across a longer span. In this study, it was investigated to what extent the relationship, in terms of coefficient of determination (R2), between strength and localized MOE was dependent on the length across which the MOE was determined. Localized MOE was calculated with MOE profiles based on dot laser scanning of fiber directions, axial dynamic excitation, and a scheme of integration across a board's cross-section. Two board samples were investigated. Maximum R2 values, which were as high as 0.68 and 0.77, respectively, were obtained for localized MOE determined across lengths corresponding to about half the depth of the investigated boards. Consequently, application of a highly localized bending MOE as an IP will result in very competitive grading.

  • 49.
    Oscarsson, Jan
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE). SP Technical Research Institute of Sweden.
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Optimization of machine strength grading of structural timber by means of bending MOE profiles with high resolution2013Ingår i: Proceedings of the 18th International Nondestructive Testing and Evaluation of Wood Symposium, Madison, Wisconsin, USA, September 24−27, 2013, Madison: USDA (United States Department of Agriculture), Forest Service, Forest Products Laboratory , 2013, s. 396-403Konferensbidrag (Refereegranskat)
    Abstract [en]

    Most machine strength grading methods are based on rather poor statistical relationships between edgewise bending strength and modulus of elasticity (MOE), the latter determined either as flatwise bending MOE measured over a length of about one meter, or as global axial dynamic MOE. Furthermore, European Standards stipulate that local MOE in both edgewise bending and tension shall be determined at a critical section and over a length of five times the depth of the piece. However, a study of tensile strain fields determined on side board surfaces using contact-free measurement technique showed that stiffness reduction occurs very locally. This characteristic was used for development of a new indicating property (IP) defined as local edgewise bending MOE and determined by means of scanned fibre direction fields and stiffness integration over cross-sections. A maximum coefficient of determination equal to 0.77 was obtained between strength and such an IP determined over a length of about the member’s half depth.

  • 50.
    Oscarsson, Jan
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Olsson, Anders
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Enquist, Bertil
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Strain fields around a traversing edge knot in a spruce specimen exposed to tensile forces2010Ingår i: Proceedings of the 2010 World Conference on Timber Engineering / [ed] Ario Ceccotti, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Two-dimensional strain fields around a traversing edge knot in a spruce specimen subjected to tensile loading were measured using a contact-free measuring tchnique based on digital image correlation. The strain fields were measured by consecutive load tests in which one side of the specimen was studied during each test. The objectives were to examine to what extent the strain fields could be detected, to investigate the correlation between strain fields measured on different sides of the specimen and to analyse the strain distribution around the knot. The results show that the applied technique is very useful for catching both overall and detailed information about the behaviour of knots in wood members exposed to loading. Both clear wood defects that could not have been identified by neither visual inspection nor scanning and the release of internal stresses were identified. The correlation between strain fields on different sides of the specimen was very good. The measurement results were compared with finite element calculations and the degree of correspondence was surprisingly good, considering the fact that the used model was fairly simple.

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