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  • 1.
    Berg, Sven
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Turesson, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Björnfot, Anders
    Faculty of Engineering, Department of Manufacturing and Civil Engineering, Norwegian University of Science and Technology, Gjøvik, Norway.
    In-plane Shear Modulus of Cross-laminated Timber by Diagonal Compression Test2019Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, nr 3, s. 5559-5572Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cross-laminated timber (CLT) is an engineered wood material that is used in the construction industry, e.g., for floors, walls, and beams. In cases where CLT-elements are used as shear walls, the in-plane-stiffness is an important property. For non-edge glued CLT, in-plane shear stiffness is lower than for edge-glued CLT. To evaluate the non-edge glued CLT panel’s in-plane shear modulus, the diagonal compression test and finite element (FE) simulation was used. FE-models with both isotropic and orthotropic material models were used to calculate the shear stiffness. The FE models using pure shear loads were used as a reference to determine the correct value of the shear modulus. To verify the FE simulations, diagonal compression tests were conducted on 30 CLT samples. A calibration formula was derived using the least square method for calculation of shear modulus. The formula gave accurate results. The results showed that FE simulations can reproduce the same shear stiffness as tests of non-edge glued 3-layer and 5-layer CLT panels.

  • 2.
    Berg, Sven
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Turesson, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Huber, Johannes Albert Josef
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Finite element analysis of bending stiffness for cross-laminated timber with varying board width2019Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, nr 6, s. 392-403Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    ross laminated timber (CLT) is a wood panelling building system that is used in construction, e.g. for floors, walls and beams. Because of the increased use of CLT, it is important to have accurate simulation models. CLT systems are simulated with one-dimensional and two-dimensional (2D) methods because they are fast and deliver practical results. However, because non-edge-glued panels cannot be modelled under 2D, these results may differ from more accurate calculations in three dimensions (3D). In this investigation, CLT panels with different width-to-thickness ratios for the boards have been simulated using the finite element method. The size of the CLT-panels was 3.0 m × 3.9 m and they had three and five laminate layers oriented 0°–90°–0° and 0°–90°–0°–90°–0°. The thicknesses of the boards were 33.33, 40.0, and 46.5 mm. The CLT panel deformation was compared by using a distributed out-of-plane load. Results showed that panels with narrow boards were less stiff than wide boards for the four-sided support setup. The results also showed that 2D models underestimate the displacement when compared to 3D models. By adjusting the stiffness factor k88, the 2D model displacement became more comparable to the 3D model.

  • 3. Pambou Nziengui, C.F
    et al.
    Turesson, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Odounga, B
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Moutou Pitti, R
    Dérermination des principales caractéristiques physiques et mécaniques du sapin blanc du massif central et de l'okoumé du Gabon.2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    The following study, shows on the basis of a series of tests carried out on samples of White fir species of the central massif and okume of Gabon, a database of the different physical and mechanical properties of these species. The tests are carried out indoors at room temperature, on specimens sized according to the French standard [AFN 06]. These specimens, whose physical properties are previously determined, are loaded in 4-point static bending on an electrostatic press. Then, using standardized calculation methods, a determination of the main mechanical parameters of these species is made. The results of the various comparative analyzes carried out show that there are no significant differences  between the parameters highlighted in this study for these different species despite the  difference between their growth areas.

  • 4.
    Turesson, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Berg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Impact of board width on in-plane shear stiffness of cross-laminated timber2019Ingår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 196, artikel-id 109249Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Board width-to-thickness ratios in non-edge-glued cross laminated timber (CLT) panels influence the in-plane shear stiffness of the panel. The objective is to show the impact of board width-to-thickness ratios for 3- and 5-layer CLT panels. Shear stiffnesses were calculated using finite element analysis and are shown as reduction factors relative to the shear stiffnesses of edge-glued CLT panels. Board width-to-thickness ratios were independently varied for outer and inner layers. Results show that the reduction factor lies in the interval of 0.6 to 0.9 for most width-to-thickness ratios. Results show also that using boards with low width-to-thickness ratios give low reduction factors. The calculated result differed by 2.9% compared to existing experimental data.

  • 5.
    Turesson, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Björnfot, Anders
    Department of Manufacturing and Civil Engineering, Faculty of EngineeringNorwegian University of Science and TechnologyGjøvikNorway.
    Berg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Tomasi, Roberto
    Faculty of Science and Technology, Division of Buildings, Architecture, and Environmental EngineeringNorwegian University of Life SciencesÅsNorway.
    Picture frame and diagonal compression testing of cross-laminated timber2019Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 52, nr 4, artikel-id 66Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Currently, no appropriate standard exists that describes how to determine the in-plane shear stiffness for cross-laminated timber (CLT) panels, meaning that, there is a lack of appropriate and reliable test methods. In this paper, two gross shear test methods are evaluated: a picture frame test and a diagonal compression test, which are intended to measure the shear stiffness of a whole CLT panel. This evaluation aimed to compare the shear modulus, the amount of compression/tension in the diagonal directions of the panels and the deformations of both sides of the panels. The picture frame test and diagonal compression test provides a bi- and uniaxial pre-stress, respectively. A total of 30 non-edge glued CLT panels were tested, 17 3-layer and 13 5-layer panels. The shear modulus for the 3- and 5-layer non-edge-glued panels were measured as 418 and 466 MPa, respectively, in the picture frame test. In the diagonal compression test, the shear modulus was measured to substantially higher values of 530 and 626 MPa for the 3- and 5-layer panels, respectively. In the picture frame test, panels were equally stretched along one of the diagonals as they were compressed along the other diagonal, which was not the case for panels in the diagonal compression test. The test results also showed that measuring only one side incurs a risk of over- or under-estimating the in-plane shear modulus. Compared with results from the literature, the picture frame test seems to be a more reliable test method than the diagonal compression test.

  • 6.
    Turesson, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Dosmaev, Dmitry
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Strengthening of Cross-Laminated Timber by adding aluminium plates2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wood is commonly judged as orthotropic with three material directions: longitudinal, radial and tangential. Shear stressand strain can occur in different directions on surfaces with different directions and shear stiffness is commonlydescribed by three shear moduli. Of those, the weakest shear modulus is called the rolling shear modulus.Cross laminated timber (CLT) is a rather recent and innovative engineered wood product with properties that can be improved and which still requires research. The benefits of using wood in buildings and construction are far from beingmaximized. During recent years, timber has been used for constructing higher buildings. It has been seen that previous small and acceptable movements of the building are magnified, which can create discomfort for the occupants. In these cases, the problem is the low in-plane shear stiffness of the CLT panel. One way to increase the in-plane shear stiffness is to build CLT mixed with other materials, with high modulus of shear, and by that increase the in-plane shear stiffness of the CLT panel. A practical test and finite element analysis (FEA) of the shear modulus was performed on 3-layer samples reinforced with aluminium plates. The panels were built by three layer of wooden lamellas and the aluminium plate was added between the first and second and/or second and third layer of boards. Two different thicknesses of the aluminium plate were used, 1 mm and 1.5 mm. Also, panels without aluminium plates were used as reference. Diagonal compression test was performed on the CLT panels, where the modulus of shear could be calculated. The diagonal compression method was performed based on experience from Andreolli. The panels containing aluminium plates had a higher shear modulus than panels without aluminium plates. This was concluded in both the practical testing and FEA.

  • 7.
    Turesson, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Impact of laminate directions on inplane shear stiffness of crosslaminated timber2016Ingår i: Annual Meeting of the Northern European Network for Wood Science and Engineering WSE,: a key factor on the transition to Bioeconomy, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Twenty-three finite element models of cross-laminated timber (CLT) with different laminate directions were studied. Simulations with quadratic orthotropic linear elastic finite elements were conducted. One goal was to compare in-plane shear stiffnesses for CLT blocks made up from Norway Spruce (Picea abies) boards. 3- and 5-layer CLT were studied with board sizes 25x150x1200 mm. Bloc sizes were 75x1200x1200 and 125x1200x1200 mm for 3-layer and 5-layer blocs, respectively. The first and last layers laminate directions were assumed to be in direction 0. The second and fourth layers laminate directions for 5-layer models were assumed equal and were 5, 10, 15, 30, 45, 60, 75 and 90. The middle layer was in direction 0 or 90. For 3-layer models the middle layers laminate directions were 5, 10, 15, 30, 45, 60, 75 and 90. No edge gluing was assumed and thus all side edges were allowed to separate or overlap. Glued contact surfaces were assumed to be perfectly glued with rigid glue. The results for 5-layer models showed that all models with angled second and fourth layers were stiffer than the models with 90 layers. Stiffnesses for models with angled second and fourth layers were higher when the middle layer laminate direction was 90 compared to 0. The stiffest 5-layer model was the one with laminate directions 0/45/90/45/0. This stiffness was 1.5 times the shear stiffness of a reference block with 1-layer and solid timber shear stiffness. The stiffest 3-layer model was the one with laminate directions 0/30/0. This stiffness was 0.99 times the shear stiffness of the reference bloc.

  • 8.
    Turesson, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Berg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Comparison of Cross- and Stress-Laminated Timber Bridge Decks2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Simply supported bridge decks made of cross-laminated timber (CLT) and stress-laminated timber (SLT) are compared. The decks have a constant axle load and varying span and thickness. CLT in the form of a plate is built up from an uneven number of layers of boards with crosswise varying fibre directions. SLT is built up from glulam beams with the same fibre direction placed side by side to form a plate. Both CLT and SLT have homogenised mechanical and physical properties and can be produced as large elements. This study was conducted by comparing results from finite element simulations of bridge decks made up from SLT and CLT for various bridge spans. The ratio of timber volume needed to fulfil deflection limits for CLT and SLT increased as the bridge span increased. The ratio was 1.3 for 24 m span and width 3.2 m. The transverse displacement curve was flatter for CLT compared to SLT. Longitudinal displacement curves were similar for CLT and SLT.

  • 9.
    Turesson, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Wang, Xiaodong (Alice)
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Gustafsson, Anders
    SP Technical Research Institute of Sweden, SP Sustainable Built Environment, Skellefteå, Sweden.
    Wall Heating: An Energy Efficient Solution for Wooden Buildings?2016Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, nr 1, s. 530-544Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wall heating is an alternative method for residential heating that is used in a limited part of Europe. The goal of this study was to show the feasibility of this method for the Nordic market and to provide a comprehensive picture of wall heating and its functionality compared to traditional methods, i.e. radiators and floor heating. The study was conducted using literature reviews, calculations, and a survey. Simulations were made using the computer software EnergyPlus (US Department of Energy). Results showed that placement of wall heating panels in interior walls results in a lower heat loss than placement in outer walls, and that wall heating can have equal or better energy-efficiency compared to floor heating and conventional radiators. Wall heating provides a more comfortable indoor climate, in regard to dust allergies, and there is no need to remove air from each individual heating panel. A disadvantage is the need for hidden installation, which creates a problem for a safe water installation and difficulties in the attachment of fixtures. Also, the wall heating system has difficultly in handling cold drafts. Though wall heating could compete with floor heating and radiators, its disadvantages are sufficient to explain why the system is not yet used in Sweden.

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