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  • 1.
    Akter, Shaheda
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Failure envelope for interaction of stresses perpendicular to the grain with rolling shear stress in wood2018In: 6th European Conference on Computational Mechanics (ECCM 6), 7th European Conference on Computational Fluid Dynamics (ECFD 7), 11 – 15 June 2018, Glasgow, UK, 2018Conference paper (Refereed)
    Abstract [en]

    The orthotropic material property in combination with ductility in compression, brittleness in shear and tension, very low shear modulus in radial-tangential (RT) plane etc. requires anisotropic stress failure criteria, as well as their evolution with increasing strains. Three- dimensional failure criteria have been proposed for this purpose, but their validation in the RT plane with interaction of rolling shear stresses has attracted less attention. Corresponding stress interactions are however important for modelling of engineered wood-based products under compression perpendicular to the grain when taking into account influence of the annual ring structure.

    The work aims at defining failure envelopes for stresses perpendicular to the grain with rolling shear stress interaction based on experimental investigations performed on Norway spruce. The experimental set-up was realized in a biaxial testing frame and consisted of stiff steel plates to transfer load from the testing machine to wood specimen. Mechanical grips prevented rotation and uplifting of the specimen in case of pure shear and tensile loading, respectively. In addition to conventional linear variable differential transformers, a digital image correlation system was used to measure strain fields on the surface of wood specimens and steel plates. Measurements of dog-bone shaped specimens were carried out along different stress interaction paths by displacement controlled loading.

    The experimental dataset was then compared with commonly used phenomenological failure criteria, namely Tsai-Hill, Tsai-Wu [1], Norris [2] and Hoffman, as well as with regression equations from previous works [3].Experiments revealed that the stress-strain relationship under compression, shear, and biaxial loading differs in radial and tangential directions. None of the three-dimensional stress failure criteria provided good prediction of experiments under compression and rolling shear, but experimental data was closer to the regression equation proposed in [3].

  • 2.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Serrano, Erik
    Lund University.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Experimental Assessment of the Load Distribution in Multi-Dowel Timber Connections2016In: 17th International Conference on Experimental Mechanics, Rhodes, Greece, July 3-7, 2016, 2016Conference paper (Other academic)
    Abstract [en]

    An integrative, hierarchically organized testing procedure for the quantification of the load distribution in multi-dowel timber connections is presented herein. The use of contactless deformation measurement systems allowed the combination of test data from single dowel and multi-dowel connections, which gave access to the loads acting on each dowel over the full loading history. As a consequence of the anisotropic material behavior of wood, a nonuniform and progressively changing load distribution among the dowels was found.

  • 3.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria .
    Hochreiner, Georg
    Vienna University of Technology, Austria .
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Serrano, Erik
    Lund University.
    Experimental characterization of the global and local behavior of multi-dowel LVL-connections under complex loading2016In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 49, no 6, p. 2407-2424Article in journal (Refereed)
    Abstract [en]

    The thorough experimental characterization of a dowel-type connection under various combinations of bending moments and normal forces is presented in this study. Double-shear steel-to-timber connections with 12 and 20 mm steel dowels were tested in a 4-point bending test set-up. The load, between the connected steel and wood beams, was transferred by the dowels themselves and also via an additional (passive) contact device, which introduced an eccentric normal force in the timber beam. The behavior of the connections was studied at the global scale of the connection and at the local scale of the individual dowels. A non-contact deformation measurement system was used to assess the changes of the location of the center of relative rotation over the entire loading. At the same time, the head deformations of the individual dowels could be measured, giving a direct indication about the force distribution among the dowels. Due to reinforcement, connections behaved distinctly ductile with a global relative rotation of up to 3°. Pre-stressing of the contact device by a force of 40 kN yielded an even stiffer behavior. For the particular configurations tested herein, the center of rotation was found to be close to the vertical axis of symmetry of the joint and close to the top row of the dowels. Moreover, the superimposed vertical shift of the center of relative rotation in case of a delayed normal force could be quantified. © 2015 RILEM

  • 4.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Serrano, Erik
    Lund University, Sweden.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dowel deformations in multi-dowel LVL-connections under moment loading2015In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, no 3, p. 216-231Article in journal (Refereed)
    Abstract [en]

    The aim of the experimental study presented herein is the assessment and quantification of the behavior of individual dowels in multi-dowel connections loaded by a bending moment. For this purpose, double-shear, steel-to-timber connections with nine steel dowels arranged in different patterns and with different dowel diameters were tested in four-point bending. In order to achieve a ductile behavior with up to 7° relative rotation, the connections were partly reinforced with self-tapping screws. The reinforcement did not influence the global load–deformation behavior, neither for dowel diameters of 12 mm nor for 20 mm, as long as cracking was not decisive. The deformation of the individual dowels was studied by means of a non-contact deformation measurement system. Thus, the crushing deformation, that is, the deformation at the steel plate, and the bending deformation of the dowels could be quantified. In the case of 12 mm dowels, the bending deformation was larger than the crushing deformation, while it was smaller in the case of 20 mm dowels. Moreover, dowels loaded parallel to the grain showed larger bending deformations than dowels loaded perpendicular to the grain. This indicates that the loading of the individual dowels in the connection differs depending on their location.

  • 5.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Serrano, Erik
    Lund University.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Integrative experimental characterization and engineering modeling of single-dowel connections in LVL2016In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 107, p. 235-246Article in journal (Refereed)
    Abstract [en]

    In order to be able to realistically and consistently elucidate and subsequently simulate the load displacement behavior of single-dowel connections, the material behavior of the individual components, namely steel dowels and wood, needs to be investigated. The behavior of slotted-in, single-dowel steel-to-laminated veneer lumber (LVL) connections with dowel diameters of 12 and 20 mm is thoroughly discussed here in relation to steel dowel and LVL properties. In addition to connection tests at different load-to-grain directions of 0, 45 and 90, the corresponding embedment behavior of LVL was tested up to dowel displacements of three times the dowel diameter. The material behavior of steel dowels was studied by means of tensile and 3-point bending tests and accompanying finite element simulations. A pronounced nonlinear behavior of the single-dowel connections was observed for all load-to-grain directions. In case of loading perpendicular to the grain, a significant hardening behavior was obvious. Due to the anisotropic material properties of wood, enforcing a loading direction of 45 to the grain resulted in an additional force perpendicular to the load direction which was quantified in a novel biaxial test setup. Thus, a comprehensive and consistent database over different scales of observations of dowel connections could be established, which subsequently was exploited by means of engineering modeling. The comparison of experimental and numerical data illustrates the potential of the engineering modeling approach to overcome drawbacks of current design regulations, which are unable to appropriately predict stiffness properties of dowel connections. Moreover, the quasi-elastic limit of dowel connections was calculated and discussed by means of the model. (c) 2016 Elsevier Ltd. All rights reserved.

  • 6.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vessby, Johan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Path dependence in OSB sheathing-to-framing nailed connection revealed by biaxial testing2018In: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 144, no 10, article id 04018197Article in journal (Refereed)
    Abstract [en]

    OSB sheathing-to-wood framing connection, as typically used in light-frame shear walls, was experimentally examined in a novel biaxial test setup with respect to possible path dependence of the load-displacement relation. The connection with an annular-ringed shank nail was loaded under displacement control following nine different displacement paths within the sheathing plane, which coincided at a number of points. In intersection points, resultant connection force, its orientation and work performed on the connection system to reach the specific point were calculated and compared. Evaluation of experiments revealed significant path dependence with respect to orientation of force resultants at path intersection points. However, magnitude of the forces and the work carried out showed relatively small dependence of the displacement path undertaken. Comparison of uniaxial connection tests with the European yield model demonstrated strong contribution of withdrawal resistance of the ringed shank nail to its lateral strength. Results of this type are a valuable basis to build better models when simulating such connections in wood structures.

  • 7.
    Blyberg, Louise
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Serrano, Erik
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sterley, Magdalena
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Adhesive joints for structural timber/glass applications: Experimental testing and evaluation methods2012In: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 35, p. 76-87Article in journal (Refereed)
    Abstract [en]

    A study of three different adhesives, silicone, acrylate and polyurethane, intended for adhesive joints in structural timber/glass applications is presented in this paper. Intentionally, adhesives with a wide range of properties were chosen. The adhesive bonds between timber and glass were tested both in tension and in shear with a bond area of 800 mm2. Special fixtures were designed both for gluing and testing the specimens. The results include strength and failure type of the adhesive bond as well as deformation of the bond lines, measured with LVDTs and a non-contact optical 3D-deformation measuring system used in combination with finite element modelling in order to obtain detailed information about the behaviour.

    Of the tested adhesives, the acrylate (SikaFast 5215) provided the largest strength, both in tension and shear. The mean strength obtained for this adhesive bond was 3.0 MPa in tension and 4.5 MPa in shear.

    Further, it is demonstrated how rotations in the specimen during the test can be detected with the optical measuring system and how finite element modelling can be used to study the stress distribution internally in the adhesive bond. One conclusion obtained from the combination of results from the optical measuring system and finite element modelling is that the behaviour of the silicone adhesive is highly influenced by its near incompressible behaviour.

  • 8.
    Blyberg, Louise
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Serrano, Erik
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sterley, Magdalena
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Timber/Glass Adhesive Bonds: Experimental testing and evaluation methods2010Report (Other academic)
    Abstract [en]

    Both timber and glass are materials that have aesthetically pleasing properties. An appealing idea is to combine them to overcome the drawbacks and utilise the beneficial mechanical properties. Adhesive bonding with an appropriate adhesive could provide a uniform stress distribution at the transition between the materials.

    This report presents a study of three different adhesives, silicone, acrylate and polyurethane. Intentionally, adhesives with a wide range of properties were chosen. The adhesive bonds between timber and glass were tested both in tension and in shear with rather small bonds, 800 mm2. Special fixtures were designed both for gluing and testing of the adhesive bond specimens studied. The results presented include a traditional study of strength, failure type and relative displacement measured with LVDT’s, but also an extended study with a non-contact optical 3D-deformation measuring system and finite element modelling.

    Of the adhesives tested, the acrylate (SikaFast 5215) performed best, both in tension and shear. The mean strength obtained for this adhesive was 3.0 MPa in tension and 4.5 MPa in shear. Even if an important factor when gluing glass is the load distribution ability, the flexible silicone adhesive has too low stiffness and strength for use in structural components, where structural refers to the ability of a component to carry loads other than its own weight.

  • 9.
    Bolmsvik, Åsa
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Stiffness and damping evaluation of Elastomers in different setups2015In: Proceedings of the Internoise 2015 conference, Society of Experimental Mechanics (SEM) , 2015Conference paper (Refereed)
    Abstract [en]

    In timber buildings, elastomers are commonly used to decrease the sound transmission between apartments. Detailed properties of the elastomers are needed in order to model them in a correct yet computational efficient manner. In earlier studies, dynamic experiments have been made on elastomer strips half embedded. However, the sidewise effects need to be further evaluated. In this study, the elastomers are evaluated quasi-statically in different directions, having continuous as well as intermittent distributions, being plane supported or half embedded. An FE-model has been developed using data stemming from the quasi-static tests together with damping estimates stemming from vibrational tests.

  • 10.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Kozłowski, Marcin
    Silesian University of Technology, Poland.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Development of large-scale load-bearing timber-glass structural elements2014In: WCTE 2014 - World Conference on Timber Engineering: Proceedings, 2014Conference paper (Refereed)
    Abstract [en]

    The building industry demands ever more effective structural elements with a multitude of requirements at the same time. There is increasing interest for load-bearing glass elements which can be deployed in timber structures, e.g. in the outer façade or as column or beam elements within the building. In an on-going research project, the materials glass, timber and the adhesive combining the former have to be selected to fit each other but also suit the application. The mechanical properties are studied individually as well as in combined small-scale specimens experimentally. Furthermore,large-scale tests on beams and shear walls are performed. This is accompanied by numerical analysis to study a wide range of dimensions and variations as well as specific design situations. The final output of the project will be prototypes to beused in showcase projects.

  • 11.
    Ehlers, Sören
    et al.
    Ship Laboratory, Helsinki University of Technology.
    Enquist, Bertil
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Uniaxial tensile of steel dog-bone specimens2007Report (Other academic)
    Abstract [en]

    This test report describes the test arrangement and the results of 4 sets of tensile specimens tested under uniaxial tension. The Aramis 4M optical strain measuring system was used to study the necking phenomena. Strain histories for a large area of the specimen over the entire range of the test are obtained and presented. The manufactures given yield strengths were 235 MPa and 275 MPa, for the nominal thickness's of 4 mm and 6 mm respectively. The specimen dimensions were according to classification society's standards and of non standard geometry. The usage of optical strain measuring system entails very satisfactory information of the whole testing process, respectively the deformation distribution. This report shall serve as a basis reference for future research in the field of metal deformation analysis. True stress versus strain curves can be derived accurately and a comparison between the clamping displacement versus Aramis displacement at a certain point can be made based on the presented results.

  • 12. Eriksson, Jerry
    et al.
    Ludvigsson, Mikael
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Load bearing timber glass composites: A WoodWisdom-Netproject for innovative building system2013In: COST Action TU0905 Mid-term Conference on Structural Glass / [ed] Jan Belis; Christian Louter; Danijel Mocibob, Boca Raton, Fla: CRC Press, 2013Conference paper (Refereed)
    Abstract [en]

    The aim of this three year project, which is part of the WoodWisdom-Net researchprogram, is to develop an innovative load bearing building system composed of timberglasscomposites. The structural loads applied onto these composites will be transferred to, andsupported by, the glass component, in contrary to today’s traditional solutions where glass elementsonly function as an environmental shield. Using such structural elements will make itpossible to largely increase the glass surface in buildings, allowing the presence of more naturallight in personal homes and office buildings.

    Timber-glass shear walls and beams will be developed taking into consideration long-term behaviorand seismic performance. Design concepts, feasibility studies and performance assessmentsof these components will be performed in order to improve the overall performance. Theproject also includes the development of new design calculations as well as the optimization ofmanufacturing methods.

    Material properties of timber, glass and adhesives will be determined from small and large scaleexperimental investigations, and will be used as input for theoretical calculations and modelingwork. The projects industrial partners will function as expertise and take part in the developmentand construction of demonstration objects.

    The project consortium is composed of academic and industrial partners from Austria, Sweden,Germany, Turkey, Slovenia, Chile, and Brazil. This paper presents material specifications andresults from small scale testing performed by the Swedish project partners.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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.

  • 16.
    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. 

  • 17.
    Kozłowski, Marcin
    et al.
    Silesian University of Technology, Poland.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology. Lund University.
    Experimental investigation on timber-glass composite I-beams2014In: Challenging Glass 4- Structural Glass-Novel design methods and next generation products / [ed] Louter, Bos, Belis and Lebet, Taylor & Francis Group, 2014Conference paper (Refereed)
    Abstract [en]

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

  • 18.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Oscarsson, Jan
    SP Sveriges Tekniska Forskningsinstitut.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Nytt paradigm för hållfasthetssortering av konstruktionsvirke: Projektrapport ett2013Report (Other academic)
    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.

  • 19.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology. SP Sveriges Tekniska Forskningsinstitut.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Nytt paradigm för hållfasthetssortering av konstruktionsvirke: Projektrapport två2014Report (Other academic)
    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.

  • 20.
    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.

  • 21.
    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.

  • 22.
    Oscarsson, Jan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    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.
    Determination of tensile strain fields in narrow Norway spruce side boards as a basis for verification of new machine strength grading methodsManuscript (preprint) (Other academic)
    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.

  • 23.
    Oscarsson, Jan
    et al.
    SP Technical Research, Institute of Sweden, Växjö.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Improving Strength of Glulam Laminations of Norway Spruce Side Boards by Removal of Weak Sections Using Optimized Finger Jointing2014In: Materials and Joints in Timber Structures: Recent Developments of Technology / [ed] Simon Aicher; H.-W. Reinhardt ;Harald Garrecht, Springer, 2014, p. 801-811Conference paper (Refereed)
    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.

  • 24.
    Oscarsson, Jan
    et al.
    SP Technical Research Institute of Sweden.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Localized modulus of elasticity in timber and its significance for the accuracy of machine strength grading2014In: Wood and Fiber Science, ISSN 0735-6161, Vol. 46, no 4, p. 489-501Article in journal (Refereed)
    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.

  • 25.
    Oscarsson, Jan
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology. SP Technical Research Institute of Sweden.
    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.
    Optimization of machine strength grading of structural timber by means of bending MOE profiles with high resolution2013In: 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, p. 396-403Conference paper (Refereed)
    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.

  • 26.
    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.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Strain fields around a traversing edge knot in a spruce specimen exposed to tensile forces2010In: Proceedings of the 2010 World Conference on Timber Engineering / [ed] Ario Ceccotti, 2010Conference paper (Refereed)
    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.

  • 27.
    Oscarsson, Jan
    et al.
    SP Technical Research Institute of Sweden, Videum Science Park, 351 96, Växjö, Sweden .
    Olsson, Anders
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Strain fields around knots in Norway spruce specimens exposed to tensile forces2012In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 46, no 4, p. 593-610Article in journal (Refereed)
    Abstract [en]

    Two-dimensional strain fields around knots in two Norway spruce specimens subjected to tension loading were detected using a contact-free measuring technique based on white-light digital image correlation. The first specimen included a traversing edge knot and the second one a centric knot. The development of strain fields as function of load level were measured by consecutive cyclic load tests in which one side of a 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 a specimen, and to analyse the strain distributions around the knots. 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. Clear wood defects that could not have been detected by neither visual inspection nor scanning were observed and conclusions could be drawn regarding release of internal stresses. The correlations between strain fields on different sides of the specimens were excellent and the correspondence between measurement results and comparative finite element calculations was surprisingly good, considering the fact that the employed FE models were fairly simple.

  • 28.
    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.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Tensile strain fields around an edge knot in a spruce specimen2010In: Proceeedings of the Final Conference of COST Action E53, 4−7 May, Edinburgh, Scotland, 2010, 2010Conference paper (Other academic)
    Abstract [en]

    Strain fields around a traversing edge knot in a spruce specimen subjected to tensile loading were measured using a contact-free measuring technique 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 1. to what extent the strain fields could be detected, 2. the correlation between strain fields on different sides of the specimen, and 3. the strain distribution around the knot. It was shown 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 detected by visual inspection or scanning and the release of internal stresses were identified. The correlation between strain fields on different sides of the specimen was very good. The correspondence between measurement results and comparative finite element calculations was surprisingly good, considering the fact that the used model was fairly simple.

  • 29.
    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.

  • 30.
    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.

  • 31.
    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.

  • 32.
    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.

  • 33.
    Oscarsson, Jan
    et al.
    SP Technical Research Institute of Sweden.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Identification of weak sections in glulam beams using calculated stiffness profiles based on lamination surface scanning2014In: Proceedings of the 2014 World Conference on Timber Engineering, Quebec, Canada, 10-14 August, Université Laval , 2014Conference paper (Refereed)
    Abstract [en]

    Models for estimation of structural properties of glued laminated timber (glulam) are generally based on the relationship between properties of the individual laminations and the properties of the glulam. In this investigation, a recently presented machine strength grading method based on laser scanning of fibre direction fields was applied for determination of axial modulus of elasticity (MOE) profiles along glulam laminations. These profiles were then used to calculate edgewise bending MOE (EB) profiles of glulam beams. The objectives were to investigate the relationship between position of bending failure and position of lowest EB value along investigated beams, and the relationship between the mentioned EB value and bending strength of the beams. It was found that both relationships were rather weak, whereas local bending MOE determined in accordance with EN408 was predicted with high accuracy on the basis of EB profiles.

  • 34.
    Petersson, Hans
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Bengtsson, Tomas
    Blixt, Johan
    Enquist, Bertil
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Källsner, Bo
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Serrano, Erik
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sterley, Magdalena
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Oscarsson, Jan
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Högre värdeutbyte genom våt- och torrlimning av sågade sidobrädor till egenskapsoptimerade träprodukter för byggmarknaden2009Report (Other (popular science, discussion, etc.))
    Abstract [en]

    The purpose of this project was to investigate the possibilities to manufacture wet-glued laminated beams for load bearing applications from Norway spruce side board lamellae and by that achieve products that are difficult to obtain from the centre yield of a log and also contribute to increased profitability in the sawmill industry.

     

    Properties such as shape stability, strength and stiffness of wet glued beams with crosssectional dimensions 50×300 mm2 and lengths 4850 and 5200 mm were analysed and compared with corresponding dry glued products. The results obtained are very promising. espite the fact that the beams were produced from a batch of unsorted boards, the performed tests showed that the product has the necessary qualities to be competitive in relation to both glued laminated timber of grade L40 and structural strength graded timber of grade C35. Requirements concerning limitations for geometrical characteristics as expressed in a proposal for a new harmonised glulam standard are also met.

     

    The bond line of the wet glued beams was analysed regarding mechanical properties such as fracture energy, local strength and wood failure percentage after cyclic boiling and drying treatments. The results showed that the bonds are able to comply with requirements concerning bond lines to be used in indoor as well as outdoor constructions for structural pplications.

     

    To be able to improve the quality of boards for use as lamellae in wet glued beams, a method for scanning the slope of grain and disturbance of grain on board surfaces was also further developed and implemented.

  • 35.
    Serrano, Erik
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Blixt, Johan
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Oscarsson, Jan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sterley, Magdalena
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Petersson, Hans
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Wet glued laminated beams using side boards of Norway spruce2011Report (Other academic)
    Abstract [en]

    In a previous research project, carried out during the years 2006-2008, the possibility to manufacture wet glued laminated beams using ungraded laminations of Norway spruce side boards was investigated with very promising results.

    In the project presented in this report, the performance of the wet glued beams has been further investigated and developed as regards grading of side board laminations, bond line properties and lamination finger jointing. The possibility to use scanning equipment for measurement of fibre angles and prediction of strength and stiffness of boards and beams has been studied and the procedures for technical approval and CE marking have been probed into. Studies concerning market and economy for the beams and layouts for a pilot plant and a full capacity plant, respectively, for production of such beams have also been carried out.

    The possibility to grade side boards in the wet state using axial dynamic excitation was investigated with a positive result. From such excitation, a board’s stiffness (modulus of elasticity) could be determined. Accordingly, grading criteria regarding axial stiffness, and knot size, was applied to grade side board laminations into two classes; outer and inner laminations. Strength and stiffness tests of beams manufactured from such graded laminations showed that the beams actually could challenge first rate glulam and LVL products available on the market.

    Regarding beam shape and shape stability, cross section cupping may need further attention. Even if this deformation was small, it was still visible to the naked eye. The problem could probably be overcome if the beams are dried to a moisture content of 12-14% before planing.

    Results of shear tests show that green glued bond lines can fulfil strength requirements for glulam. However, delamination requirements for service class 3 (outdoors) were not fully met. From small scale tensile testing of glued bonds it was concluded that green glued bonds with high density wood have the same tensile strength and fracture energy as dry glued bonds. For bonds with low density wood and/or small amount of adhesive, the tensile strength could be lower than for dry glued bonds, whereas the fracture energy was on a similar level.

    Strength testing of wet and dry glued finger joints demonstrated that joints glued from high density wood was significantly stronger than low density joints and that there was no significant difference between the strength of green glued joints and joints glued after drying. From X-ray measurement it was shown that the glue penetration into the wood fibres is much deeper in a green glued joint than in a joint that is glued in the dried state.

    From scanning algorithms developed within the scope of this project it is possible to obtain reasonably accurate predictions of grain-angle distributions on board surfaces as well as rather accurate descriptions of knot locations and of fibre-angle disturbances around knots. From scanning of board ends, cross section characteristics with respect to radial and tangential directions and of annual ring widths could also be determined. Finally, both board and beam stiffness were predicted from this data, with an accuracy that is comparable with the one obtained from well-reputed commercial grading systems.

  • 36.
    Serrano, Erik
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Load-bearing timber-glass shear walls2014In: Glass | Facade | Energy / [ed] Schneider, Jens and Weller, Bernhard, Technische Uni Dresden , 2014, p. 311-318Conference paper (Refereed)
    Abstract [en]

    Timber-glass composite shear wall elements were manufactured with different adhesives. The elements were 1200×2400 mm in size. 12 single pane elements and one element with an insulation glass unit (IGU) were manufactured. The load bearing glass pane was in all cases made from 10 mm float glass. The elements were tested in various loading conditions, involving pure vertical load and different combinations of in-plane shear and vertical loading. The test results show that the influence of the adhesive chosen on the ultimate (buckling) load is only of minor importance. This was also confirmed by finite element analyses.

  • 37.
    Serrano, Erik
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Compression strength perpendicular to grain in cross-laminated timber (CLT)2010In: World Conference on Timber Engineering, 2010Conference paper (Refereed)
    Abstract [en]

    The work presented involved testing of the compression strength of square specimens made from threelayer CLT. In one of the test set-ups a uniform compression over the complete square face of the specimen was used - similar to what is defined in the current European test standard for glued-laminated timber. In addition, several other test set-ups involving loading of only parts of the specimens’ square surface by line loads was investigated. The use of line loads aimed at investigating the effect of load distribution within the test specimen, and also to investigate possible boundary effects when the line load is applied close to the specimen edge. In practical design, the line load used in the tests, would correspond to the load transfer from a wall structure clamping a CLT-slab. During testing, apart from registering the load and deformation by conventional gauges, a contact-free deformation measurement system was used.

    The results show that the compression strength – defined according to Eurocode 5 as the load at which a 1% permanent set is obtained – is indeed dependent on the relative size of the load application area, its orientation relative to the surface grain direction and its distance to the edge of the specimen. Other conclusions are that test methods, test evaluation methods as well as design criteria for compression perpendicular to grain in CLT should be revisited.

  • 38.
    Serrano, Erik
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Lund University ; SP Technical Research Institute of Sweden.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vessby, Johan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Long term in-situ measurements of displacement, temperature and relative humidity in a multi storey residential CLT building2014In: WCTE 2014 - World Conference on Timber Engineering, Proceedings, 2014Conference paper (Refereed)
    Abstract [en]

    In a multi-storey residential housing project comprising of four 8-storey timber buildings, the bottom storeybeing designed with concrete and storeys 2-8 in timber, the vertical relative displacement, the temperature and the relativehumidity (RH) along one vertical channel in the external wall of one building has been monitored. Measurements startedduring construction and presented herein are results of 6.5 years of in-situ measurements. Displacement data was monitoredstorey-by-storey, with a sampling frequency of 1 measurement every 10-60 minutes. In another of the four buildingsadditional temperature and relative humidity measurements have been ongoing for about 5.5 years. These temperature andRH measurements were performed at six different locations in the building, at each location in eight positions through theexterior wall with a sampling frequency of 1 measurement every 15 minutes. The results show that the total verticaldisplacement over six storeys after 6.5 years of service life is approximately 23 mm as a yearly average, and over the yearthe displacement varies from this value by approximately ±2 mm. The main cause for the relative displacement is thedecrease of moisture content in the wood material leading to shrinkage after completion of the building. The resultsobtained show also that the exterior wall design of the building behaves well in terms of not comprising a general risk fordamp or mould in the timber core of the external walls.

  • 39.
    Serrano, Erik
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Vessby, Johan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Vertical relative displacements in a medium-rise CLT-building.2010In: Structures and Architecture / [ed] Paulo J.S. Cruz, 2010Conference paper (Refereed)
  • 40.
    Serrano, Erik
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Oscarsson, Jan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sterley, Magdalena
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Petersson, Hans
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Green-glued laminated beams: High performance and added value2010In: World Conference on Timber Engineering, 2010Conference paper (Refereed)
    Abstract [en]

    The work presented in this paper deals with the use of green gluing (also known as wet gluing) as a mean to overcome the difficulties in making use of side boards for structural applications. By manufacturing laminated beams from unseasoned side boards several advantages are obtained. Beams were manufactured from side boards of approximately 25 mm thickness. The board width was 120 mm. The boards were glued together with a 1-component polyurethane adhesive to form a beam cross-section of approximately 120×315 mm2. After curing, the beams were split into two halves, each approximately 55 mm wide. These 55×315 mm2 beams were then dried in a conventional kiln dryer. Finally, the beams were planed to target size, 50×300 mm2. Tests performed included beam bending tests for strength and stiffness, tests of the shape stability of the beams, tests of the integrity of the adhesive bond lines (delamination) and tests on the strength and fracture energy of the adhesive bond lines. The main results obtained show that there is a potential for the production of green-glued laminated beams with good technical performance.

  • 41.
    Serrano, Erik
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. SP Technical Research Institute of Sweden, Borås.
    Oscarsson, Jan
    SP Technical Research Institute of Sweden, Borås.
    Sterley, Magdalena
    SP Technical Research Institute of Sweden, Borås.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Green-Glued Products for Structural Applications2014In: Materials and Joints in Timber Structures: Recent Developments of Technology, Springer, 2014, p. 45-55Conference paper (Refereed)
    Abstract [en]

    The results from bending tests on 107 laminated, green-glued, beams manufactured from Norway spruce side boards are presented. The beams were made by face gluing 21-25 mm thick boards using a commercial one-component moisture curing polyurethane adhesive. In addition to the bending test results, results from shape stability measurements after climatic cycling and bond line strength and durability test results are also presented. The results from the bending tests show that, by applying very simple grading rules, it is possible to obtain beams with high bending strength (with a 5%-percentile characteristic value of 40,1 MPa) and substantial stiffness (mean value of 14360 MPa). Also the shape stability of the beams and the strength and the durability of the interlaminar bonds were found to be satisfactory.

  • 42.
    Sjödin, Johan
    et al.
    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.
    Contact-free measurements and numerical analyses of the strain distribution in the joint area of steel-to-timber dowel joints2006In: Holz als Roh- und WerkstoffArticle in journal (Refereed)
    Abstract [en]

    Two different dowel-type joints of differing size were loaded in tension parallel to the grain. The strain distribution in the joint area was studied using a contact-free measurement system. The results were compared with those of numerical analysis. The measurement system was found to be a valuable complement to traditional measurement techniques and also to numerical analyses performed in parametric studies. The measurements obtained were shown to be particularly useful for studying the highly nonlinear behavior of timber that is of special importance in characterizing timber dowel joints.

    Several observations of considerable interest were made on the basis of numerical results in combination with results of the contact-free measurement system. A non-uniform strain distribution in the joint area was detected, for example, and shear strains and tensile strains, both parallel and perpendicular to the grain were found to be concentrated in the areas most likely to influence the failure mode of the joint. A general observation made was that the larger size joint failed in brittle manner, an observation supported by previous research.

  • 43.
    Sjödin, Johan
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Serrano, Erik
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Enquist, Bertil
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    An experimental and numerical study of the effect of friction in single dowel joints2008In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 66, no 5, p. 363-372Article in journal (Refereed)
    Abstract [sv]

    The effect of friction between the dowel and the surrounding timber was studied for single dowel-type joints. The joints tested were divided into two groups of joints, where the surface of the dowels differed. For the first group, the dowels had a smooth surface and for the second group the dowels had a rough surface. A contactfree measurement technique was used in the experimental investigation. In addition to that, numerical simulations were carried out aimed at predicting the load-bearing capacity of the joints tested as well as estimating the coefficient of friction between the dowel and the surrounding timber.

    Important conclusions from this study, which are supported by previous research, are that the load-bearing capacity of single dowel-type joints increases when the surface roughness of the dowel increases. A very small scatter in the results, in terms of the load-displacement behavior, was seen in the tests with rough surface dowels. For the joints with smooth surface dowels, the elastic response as well as the plastic response varied considerably between different tests. The current version of the European timber code EC5 does not explicitly take into account the effect of friction. In order to take the effect into account embedding tests have to be performed in order to be able to consider the benefits of using dowels with rough surface.

  • 44.
    Sterley, Magdalena
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Serrano, Erik
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Enquist, Bertil
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Flat wise green gluing of Norway spruce for structural application2009In: International Conference on Wood Adhesives 2009 / [ed] Charles Frihart, Madison: Forest Products Society, 2009, p. 325-334Conference paper (Refereed)
    Abstract [en]

    Unseasoned (green) Spruce timber planks with dimensions25 x 150 x 5400 mm3 were flat-wise glued with a one-componentPUR adhesive, forming laminated beams with 150 x 300 mm2 crosssection.After curing, each beam was divided in two halves and subsequentlydried. The final cross-section of the beams was thus 50 x 300mm2. The evaluation of the beams included bending stiffness andbending strength in 4-point bending and the mechanical properties ofthe adhesive bonds. The adhesive bonds were tested according toEuropean standards for glued-laminated timber (EN 392, EN 391) andaccording to ASTM D 905, but also with a special small-scale specimenfor testing the fracture properties of the adhesive bond in Mode I.The complete force vs. deformation curve, including both the ascendingand the descending parts could be obtained. The deformationswere measured with a contact-free technique, based on two camerasand white light. The equipment made it possible to register the strainin the bond line and in the adjacent wood with a high spatial resolution(0,2 mm). The strength of the bond line and the fracture energywas calculated. Results show that both the stiffness and the strength ofthe beams can comply with the requirements for glued-laminated timberclass L40. The adhesive bonds fulfill the requirements of glulam instandard EN 386. The tensile strength and fracture energy measuredwith the small specimens of green-glued bond lines is on the samelevel as of conventionally glued bond lines.

  • 45.
    Sterley, Magdalena
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Serrano, Erik
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Enquist, Bertil
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Fracture characterisation of green glued polyurethane adhesive bonds in Mode I2008In: Enhancing bondline performance.: Proceedings of the Final Conference in COSTE 34, Cost Action E34, Sopron , 2008, p. 156-166Conference paper (Other academic)
  • 46.
    Sterley, Magdalena
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Fracture characterisation of green glued-polyurethane adhesive bonds in Mode I2013In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 46, no 3, p. 421-434Article in journal (Refereed)
    Abstract [en]

    Unseasoned (green) spruce timber side boards of size 25 × 120 × 600 mm were flatwise-glued with a one-component PUR adhesive. Glued pairs of boards were then kiln-dried to 12 % moisture content. A special small-scale specimen for testing the fracture properties of the adhesive bond in Mode I was developed in order to evaluate the adhesive bond properties. The complete force versus deformation curve, including both the ascending and the descending parts, could be obtained with these small-scale specimens, enabling the strength and fracture energy of the bond line to be calculated. In addition, the fractured specimens were examined by scanning electron microscope. Results show that both the tensile strength and the fracture energy of the green glued PUR adhesive bonds were equal to those of the dry glued bonds. The methodology developed and used in the present study gives new possibilities for analysis of the mechanical behaviour of wood adhesive bonds, and particularly of their brittleness and its correlation with the type of fracture path. This is in sharp contrast to the use of standardised test methods (e.g. EN 302, ASTM D905) with specimens having relatively large glued areas. Using such types of specimens, it is not possible to obtain the complete force versus deformation response of the bond. In addition, when using such test methods, failure takes place in the wood or in the fibres near the bond, thus making it impossible to obtain detailed information about the bond line characteristics.

  • 47.
    Sterley, Magdalena
    et al.
    SP Technical Research Institute of Sweden, Stockholm.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology. SP Technical Research Institute of Sweden, Stockholm.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Hornatowska, Joanna
    Innventia AB, Stockholm.
    Finger jointing of freshly sawn Norway Spruce side boards: a comparative study of fracture properties of joints glued with phenol-resorcinol and one-component polyurethane adhesive2014In: Materials and Joints in Timber Structures: Recent Developments of Technology, Springer, 2014, p. 325-339Conference paper (Other academic)
    Abstract [en]

    Finger jointing of unseasoned Norway Spruce was studied with respect to tensile strength, adhesive penetration and durability. Finger joints were manufactured with 1) unseasoned wood and one component polyurethane (PUR) adhesive, 2) dried wood and PUR adhesive and 3) dried wood and phenol resorcinol formaldehyde (PRF) adhesive. Two levels of wood density were used. The tensile strength of the finger joints was determined and the deformations within the joint were studied with an optical measurement system (ARAMIS). The penetration of the adhesive was studied with x-ray microtomography. The durability of the joints was determined according to the standard ASTM D 4688. The results show that the tensile strength and the durability of green glued finger joints are on the same level as that of dry glued PUR joints. The penetration of the PUR adhesive is high in the unseasoned wood and cavities within the bonds seem to be smaller than in dry glued PUR joints. The tensile strength of the finger joints is dependent on density, independent on the adhesive system used. The strength of the green glued PUR adhesive bonds in finger joints measured with small scale specimens did not differ from the strength of the dry glued PUR bonds.

  • 48.
    Vessby, Johan
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Directional dependency in an OSB sheathing-to-framing mechanical connection2014Conference paper (Refereed)
    Abstract [en]

    Nailed connections are commonly employed for connecting sheathings to the framing used in shear walls. Although many aspects of such connections have been investigated thoroughly within the research community generally, the effect the loading direction has on connections of this sort has been much less investigated. In the present study experimental tests were carried out for determining in detail the effects the loading has on different sheathing-to-framing connections. The results obtained indicated the degree of loading to which a nail fastened to an oriented strand board (OSB) sheathing is subjected to not be strongly affected by which of the two main loading directions is involved, but that the effects of loading direction are found to be much greater if the timber element in question is also included in the testing carried out. The dependency of the loading effect on the loading direction at different loading stages and for different directions - parallel to the fibres, perpendicular to them, at some angle between these two main directions - was investigated here.

  • 49.
    Vessby, Johan
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Enquist, Bertil
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Petersson, Hans
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Alsmarker, Tomas
    Experimental study of cross-laminated timber wall panels2009In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 67, no 2, p. 211-218Article in journal (Refereed)
    Abstract [en]

    The use of cross-laminated structural timber elementsis becoming increasingly popular. The number of layersvaries normally from three upwards. The structural performanceof five-layer cross-laminated timber elements was investigated.The five layers consisted of 19mm thick boards,laid successively at right angles to each other and gluedtogether with PU-adhesive, layers 1, 3 and 5 lying in onedirection and layers 2 and 4 in the other. The stiffness andstrength of four cross-laminated timber elements (4955mmlong, 1250mm wide and 96mm thick) were studied duringin-plane bending. Two of the elements were first partitionedinto two parts that were reconnected in two different waysprior to testing. The influence of the way in which the crosslaminatedtimber elements were reconnected was studied,the behaviour observed being compared with the test resultsfor the unpartitioned specimens with respect to both strengthand stiffness. The experimental tests performed showed thecross-laminated timber elements to possess a high degree ofstiffness and strength. There was also found to be a markeddifference in behaviour between the two different ways inwhich the elements were connected to each other. One of thetwo connecting methods studied, being of less good designbut earlier frequently used in Sweden, showed as expectedpoor structural performance, whereas the other one appliedas a safer alternative performed well.

  • 50.
    Vessby, Johan
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Olsson, Anders
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Enquist, Bertil
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Contact-free strain measurement of bi-axially loaded sheathing-to-framing connection2008In: 10:th World Conference on Timber Engineering, 2008Conference paper (Refereed)
12 1 - 50 of 51
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