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1.
  • Larsson, Magnus, et al. (author)
  • Novel Processes for Architectural Optimisation of Building Materials Performance: Introducing Material Phase Transitions and Generative Life Cycle Assessments
  • Journal article (peer-reviewed)abstract
    • Conventional phase diagrams plot differences in properties (e.g. volume) of a medium generated by changes in external conditions (e.g. temperature and/or pressure). This paper discusses how the logic of such diagrams can be applied to produce a new type of surface plot, material phase transition (MPT) diagrams, that chart not the conditions for chemical equilibrium but the relative benefits of a particular material system given a set of predefined objectives and a virtual search space of design solutions. Such diagrams can form an integral part of parametric design processes that use ‘auxiliary loads’ (e.g. LCA values) as variables to generate design iterations. A Grasshopper user object is created and used to design a box beam that yields a set of auxiliary loads charts and MPT diagrams. The anatomy of MPT diagrams is described, and areas for future studies discussed.
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2.
  • Larsson, Magnus, et al. (author)
  • Optimisation of timber structures based on weighted objectives
  • 2017
  • In: Proceedings of the 13th annual meeting of the Northern European Network for Wood Science and Engineering , September 28-29. ; , s. 79-84
  • Conference paper (other academic/artistic)abstract
    • Contextual optimisation workspace (COW) is a digital design tool under developmentthat seeks to promote novel processes for the parametric design of architectural andengineering structures using multiple-objective optimisation (MOO) strategies based onevolutionary algorithms. Assembled within the Grasshopper (GH) graphical algorithmeditor, the tool allows for constructive analytical comparisons between often conflictingaspects of a design that have historically been assumed incomparable, with the resultingcompromises between objectives presented as iterations of a three-dimensionalgeometry with associated data. This increases the capability to make informeddecisions throughout the design process and to control the implementation of apotentially wide range of differing design objectives. This is useful in situations wherean extended design team (more than one stakeholder) is collaborating on anarchitectural project, which would include most real-life applications. In such a team, allagents have different preferred outcomes. The effort to manage their expectations andfulfil their respective agendas becomes the aim of the resulting architectural scheme.This paper explores how the COW tool could benefit from the addition of componentsthat simplify such decision-making processes, and showcases how such additions couldbe applied to the design of timber structures. Two new GH user objects were designedthat simplify an extended and weighted control of MOO-based design actions usingCOW, while providing a mechanism that guarantees designs are not considered if theydo not meet the minimal requirements set by the constraining frame conditions. Suchstakeholder-based MOO designs are shown to be a beneficial addition to the COWsystem. It is argued that a more comprehensive version of this first attempt to allowdiffering desires to be used as a weighted part of the design process is a promisingstrategy for the design of future timber structures.
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3.
  • Larsson, Magnus, et al. (author)
  • Sliding Sidewinders: Early-Stage Design of an Anticipatory Adaptive Assemblage
  • Journal article (peer-reviewed)abstract
    • This quantitative/qualitative evaluation of meta-heuristic design processes being implemented in a real-life architecture project introduces the theoretical concept of anticipatory adaptive assemblages (AAA) and reports on tactics that were used to reduce the ‘curse of dimensionality’ associated with the mechanisms that produce such assemblages. It describes strategies to adopt ‘presilient’ methods to constrain a model’s design space before any evolutionary solving occurs, leverage the advantage in fenestration performance presumed to arise from explorations of non-periodic tessellations of the plane, and use benchmark models to optimise some material aspects of wall sections. These tactics all support a materiality-based approach to designing architecture using genetic algorithms. The experiments were designed in an attempt to begin to close the knowledge gap between on the one hand the existing praxis of LCA-based analyses, on the other simulations that use material properties to directly inform geometries associated with particular combinations of (for instance) site, weather, and material data. The hypothesis is that AAA’s can become an effective framework for design-based adaptation to site conditions and mitigation of climate change. The objectives of the study are a) to implicitly and qualitatively describe the trials and tribulations a commercial adaptation of alternative design processes may cause, while b) explicitly and quantitatively report on the results of the experiments, and how they relate to AAAs. After an introduction of the AAA concept, three design experiments are described and their outcomes analysed, followed by a concluding discussion including suggestions for future studies.
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4.
  • Larsson, Magnus, et al. (author)
  • Teleodynamic timber façades
  • 2018
  • In: Frontiers in Built Environment. - : Frontiers Media S.A.. - 2297-3362. ; 4
  • Journal article (peer-reviewed)abstract
    • This paper investigates ways in which weathering-related site conditions can be allowed to inform the design process in order to improve a building's geometry and performance. Providing a building design with the capacity to remember past experiences and anticipate future events can provide substantial gains to the architectural configuration and engineering of a timber façade. A new theory of architecture is outlined based on recent “teleodynamic” theories—a hypothesis about the way far-from-equilibrium systems interact and combine to produce emergent patterns. The proposed explanation considers nested levels of thermodynamic systems applied to an architectural context: “homeodynamic” operations that involve equilibration and dissipation of constraint combine to produce self-organising “morphodynamic” procedures that amplify and regularise site-specific constraining data streams. A teleodynamic design reconstitutes itself by combining morphodynamic processes so as to optimise its relationship to the past, present, and future. A novel teleodynamic design tool called Contextual Optimisation Workspace (COW) is assembled within the Grasshopper visual programming environment. The tool is used to carry out four experiments that combine to produce the teleodynamic design of an urban wooden façade, exemplifying an alternative framework for the design of wood-based structures. The first experiment investigates a variegated grid combining two distinct subdivision methods (an orthogonal grid and a Voronoi tessellation), transmuting one system into another. The second and third experiments focus on durability aspects of a wooden façade and devise strategies for how the effects of photochemical degradation and wetting due to driving rain might be minimised using the COW tool. The fourth experiment optimises the building for daylight based on an illuminance simulation. Using simulation and anticipation to add the advantages of site- and time-specific data streams as a design strategy can effectively suspend an algorithm-driven design iteration in time and space in order to allow it to be parametrically influenced by past or future events such as unique site and project conditions. The COW tool can be used to produce such teleodynamic designs.
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5.
  • Bryne, Lars Elof, et al. (author)
  • UV-laser irradiated wood : Some aspects on micromorphology, wettability, surface composition and liquid permeability
  • 2008
  • In: Proceedings of the 4th meeting of the Nordic-Baltic network in wood material science and engineering (WSE). ; , s. 75-82
  • Conference paper (peer-reviewed)abstract
    • Many wood products used as building or construction materials involve a combination of the wood material with polymers, such as adhesives, coatings, preservatives and binders in composites. Combinations of wood and polymers in outdoor exposure, however, in general have poor long-term durability. A major cause of the unsatisfactory durability can be related to the high hygroscopicity of wood and the great difference in hygro-thermal properties between the components, resulting in wood-polymer de-bonding. In addition, mechanical processing (e.g. sawing, sanding and planning) of wood in general forms a weak boundary layer of loose and crushed wood cells in the surface which also may interfere with the wood-polymer bonding. The main objective of this work was to study ultra violet (EV), or excimer, laser irradiation on wood as a means to remove, by ablation, the outer deformed layer from a wood substrate. Effects of the UV-laser treatment on wetting and liquid permeability characteristics were studied by Wilhelmy plate experiments, and effects on the wood surface chemistry were studied by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The micromorphology of wood was studied by low vacuum-scanning electron microscopy (LV-SEM). The pre-treatment of wood substrates by UV-laser ablation resulted in a notable changes in surface micromorphology, liquid permeability, wettability and surface chemistry characteristics.
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6.
  • Crocetti, Roberto, et al. (author)
  • Multiple shear plane connections with timber based gusset plates
  • 2021
  • In: World Conference on Timber Engineering 2021, WCTE 2021. - : World Conference on Timber Engineering (WCTE).
  • Conference paper (peer-reviewed)abstract
    • This paper presents the results of an experimental study conducted on multiple-shear joints consisting of gusset plates made of either LVL or plywood connected to the timber members by means of full-threaded self-tapping screw. Both hardwood and softwood timber based gusset plates with different thickness and face grain orientations were investigated. The results show that this type of connection has an excellent structural performance, with not very dissimilar strength from that of comparable connections which makes use of slotted-in steel plates and dowels. It is believed, therefore, that the proposed solution can be a valid alternative to the more traditional timber connection with slotted-in steel plates and dowels. 
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7.
  • Debertolis, Mattia, et al. (author)
  • Investigation on mechanical connections with birch plywood gusset plates
  • 2023
  • In: 19th Annual Meeting of the Northern European Network for Wood Science and Engineering. - Ås, Norway : The Nordic Forest Research Cooperation Commitee. ; , s. 96-98
  • Conference paper (peer-reviewed)abstract
    • The construction industry is increasingly driven by sustainability concerns, prompting a search for alternative materials with a low environmental footprint, such as engineered wood products. Nowadays, connections of timber elements are still performed by the use of steel plates. However, steel plates can be replaced by plywood made of birch since it has superior mechanical properties compared to plywood made from softwood (Wang et al. 2021, 2022; Crocetti et al. 2021; Werner Åström, 2019). Besides, the capacity calculation for this connection according to the standards is conservative, meaning that the efficiency is low and the actual capacity could be much higher than the design value (Rossi et al. 2016). This research aims to enhance the knowledge and the design process of timber-to-timber connections with birch plywood (BP) plates.
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8.
  • Englund, F., et al. (author)
  • Spectroscopic studies of surface chemical composition and wettability of modified wood
  • 2009
  • In: Wood Material Science & Engineering. - : Taylor & Francis Group. - 1748-0272 .- 1748-0280. ; 4:1-2, s. 80-85
  • Journal article (peer-reviewed)abstract
    • Recent advances in spectroscopic methods used in the surface science field may provide new valuable information about the surface chemical composition of engineering materials. Such methods, combined with wettability analyses, have been applied in the development of well-designed adhesives and coating systems for newly developed and commercially available modified wood materials. The main objective of this paper is to demonstrate and present some aspects on the application of two different state-of-the-art spectroscopic methods for surface chemical composition studies of a complex material such as modified wood. The methods are X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), the former generating more quantitative data and the latter more qualitative data. The spectroscopic data are also combined with wettability data obtained from contact angle measurements using the Wilhelmy method. Modified wood samples were prepared from pilot plant or commercially produced acetylated, furfurylated and thermally modified wood. Effects of wood surface ageing, i.e. the time after machining, on the surface chemical composition and wettability were also studied. Results clearly indicate a hydrophobization process due to ageing of the unmodified and certain modified wood, probably mainly related to a migration and reformation of extractives in the surface. The surface composition and wettability of acetylated wood was not appreciably affected by the ageing process. Such findings could be quantified by the XPS measurements, which is further discussed and related to the different wood modification routes. ToF- SIMS is a powerful tool and complementary to XPS for identification of, for example, specific hydrophobic substances in the wood surfaces. In addition, this method provides ion images, mapping the lateral distribution of selected secondary ions signals within an analysed wood surface area.
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9.
  • Falk, Andreas, 1974-, et al. (author)
  • Function and design of innovative bio-based products for the building sector
  • 2016
  • In: Structures and Architecture - Proceedings of the 3rd International Conference on Structures and Architecture, ICSA 2016. - : CRC Press/Balkema. - 9781138026513 ; , s. 93-101
  • Conference paper (peer-reviewed)abstract
    • This paper will present a study of preconditions for competitiveness in a resource saving society. Preconditions for material suppliers and industry versus requirements from legislation and consumers means a balance, which can be difficult to manage. The paper is aiming for an analysis of the preconditions for property modification, innovation and marketing of biobased materials and products, and the paper deals with strategies to release the architectural potential of bio-based construction. 
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10.
  • Gardner, D. J., et al. (author)
  • Editorial note
  • 2006
  • In: Journal of Adhesion Science and Technology. - : VSP. - 0169-4243 .- 1568-5616. ; 20:8, s. 723-723
  • Journal article (other academic/artistic)
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11.
  • Inoue, Masafumi, et al. (author)
  • Dimensional stabilization of compressed laminated veneer lumber by hot pressing in an airtight frame
  • 2008
  • In: Wood Material Science & Engineering. - : Taylor & Francis Group. - 1748-0272 .- 1748-0280. ; 3:3-4, s. 119-125
  • Journal article (peer-reviewed)abstract
    • Abstract The purpose of this study was to evaluate the dimensional stability and strength properties of compressed laminated veneer lumber (LVL) produced using a closed hot pressing system. LVL specimens were produced with varying number of veneers using either diphenylmethane diisocyanate (MDI) or a water-soluble phenol formaldehyde (PF) resin at varying temperatures (160?200°C), pressures (0.5?3 MPa) and hot-pressing times (2?16 min). Results show that the heating process decreases the recovery of compressive deformation in the veneers when subjected to cyclic moisture and heat conditions. Thickness swelling was approximately 5% after a drying, wetting and boiling cyclic test for LVL using the MDI resin and hot pressed at 200°C for 8 min. Modulus of elasticity and rupture increased for samples produced in both an open press and the closed press with an increase in the number of veneers and density, as did the absorbed energy in impact bending.
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12.
  • Källbom, Susanna (author)
  • Characterisation of thermally modified wood for use as component in biobased building materials
  • 2018
  • Doctoral thesis (other academic/artistic)abstract
    • The building sector shows growing interest in biobased building materials. Wood components, here defined as ground or milled wood, i.e. by-products (residuals/residues) from wood processing, such as sawdust or shavings, are valuable raw materials for new types of durable biocomposites suitable for outdoor building applications. An important research question related to such composites is how to characterise and enhance molecular interactions, i.e. adhesion properties, between wood and binder components. Another challenge is the hygroscopicity of the wood component, which can lead to dimensional changes and interfacial cracks during exposure to varying moisture conditions. Thermal modification of wood reduces its hygroscopicity, thereby, increasing its durability, e.g. its dimensional stability and resistance to biodeterioration. The hypothesis is that the use of thermally modified wood (TMW) components in biocomposites can enhance their durability properties and, at the same time, increase the value of residues from TMW processing. The main objective of this thesis is to study and analyse the surface and sorption properties of TMW components using inverse gas chromatography (IGC), dynamic vapour sorption (DVS), X-ray photoelectron spectroscopy (XPS), and the multicycle Wilhelmy plate method. The aim is to gain a better understanding of the surface and sorption characteristics of TMW components to enable the design of optimal adhesion properties and material combinations (compatibility) for use in biocomposites, especially suitable for outdoor and moist building material applications. Samples of TMW and unmodified wood (UW) components of Norway spruce (Picea abies Karst.) and Scots pine (Pinus sylvestris L.) heartwood were prepared and analysed with respect to surface energetics, hygroscopicity, liquid sorption and resulting swelling. The work also included analysis of surface chemical composition, as well as influences of extractives and moisture sorption history. The effect of using TMW components in a wood plastic composite (WPC) exposed to a series of soaking-drying cycles in water was studied with a focus on water sorption, swelling and micromorphological changes. The IGC analyses indicate that TMW components of spruce have a more heterogeneous surface energy character, i.e. a distinctly higher dispersive part of surface energy for low surface coverages, than do UW components. This is suggested to be due to the higher percentage of hydrophobic extractives present in TMW samples. Lewis acid-base analysis indicates that both UW and TMW components from spruce have a predominantly basic character and an enhanced basicity for the latter ones. Results show that both the hygroscopicity and water liquid uptake are lower for TMW than for UW samples. Unexpectedly, a significantly lower rate of water uptake was found for the extracted UW of pine heartwood than for non-extracted samples. In the former case, this is presumably due to contamination effects from water-soluble extractives, which increase capillary flow into wood voids, as proven by a decrease in water surface tension. Water uptake as well as swelling was significantly reduced for the WPCs with TMW and hot-water extracted UW components compared with the WPCs with UW components. This reduction also resulted in fewer wood component-polymer interfacial cracks in the WPCs with the modified wood components.
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13.
  • Källbom, Susanna, et al. (author)
  • Effects of water soaking-drying cycles on thermally modified spruce wood-plastic composites
  • 2020
  • In: Wood and Fiber Science. - : SOC WOOD SCI TECHNOL. - 0735-6161. ; 52:1, s. 2-12
  • Journal article (peer-reviewed)abstract
    • The overall aim of this work was to gain more insight on the potential of modified wood (TMW) components for use in wood-thermoplastic composites (WPCs). Laboratory-scale TMWPCs were produced, and the effects of severe water soaking-drying cycles on the samples were studied. Water sorption behavior and resulting dimensional and micromorphological changes were also studied, and the results were compared with those of unmodified wood-plastic composites (UWPCs) used as control. The TMW was prepared by cutting a spruce board into half and subjecting one-half to an atmosphere of superheated steam at atmospheric pressure with a peak temperature of 210 degrees C, with the other unmodified wood (UW) half as a control. The TMW and UW components were then prepared by a Wiley mill and thereafter sifted into smaller (mesh 0.20-0.40 mm) and larger (mesh 0.40-0.63 mm) size fractions. A portion of the wood components were also subjected to hydrothermal extraction (HE). Composite samples with these different wood components, polypropylene (PP) matrix, and maleated PP (MAPP) as coupling agent (50/48/2 wood/PP/MAPP ratio by weight) were then prepared by using a Brabender mixer followed by hot pressing. The matching micromorphology of the composites before and after the soaking-drying cycles was analyzed using a surface preparation technique based on ultraviolet-laser ablation combined with scanning electron microscopy. The results of the water absorption tests showed, as hypothesized, a significantly reduced water absorption and resulting thickness swelling at the end of a soaking cycle for the TMWPCs compared with the controls (UWPCs). The water absorption was reduced with about 50-70% for TMWPC and 60-75% for HE-TMWPC. The thickness swelling for TMWPCs was reduced with about 40-70% compared with the controls. Similarly, the WPCs with HE-UW components absorbed about 20-45% less moisture and showed a reduced thickness swelling of about 25-40% compared with the controls. These observations also were in agreement with the micromorphology analysis of the composites before and after the moisture cycling which showed a more pronounced wood-plastic interfacial cracking (de-bonding) as well as other microstructure changes in the controls compared with those prepared with TMW and HE-UW components. Based on these observations, it is suggested that these potential bio-based building materials show increased potential durability for applications in harsh outdoor environments, in particular TMWPCs with a well-defined and comparably small size fractions of TMW components.
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14.
  • Källbom, Susanna, et al. (author)
  • Sorption and surface energy properties of thermally modified spruce wood components
  • 2018
  • In: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 50:3, s. 346-357
  • Journal article (peer-reviewed)abstract
    • The objective of this work is to study the water vapor sorption and surface energy properties of thermally modified wood (TMW) components, ie wood processing residuals in the form of sawdust. The thermal modification was performed on spruce wood components using a steam-pressurized laboratoryscale reactor at two different temperature (T) and relative humidity (RH) conditions, T = 150 degrees C and RH = 100% (TMW150), and T = 180 degrees C and RH = 46% (TMW180). A dynamic vapor sorption (DVS) technique was used to determine water vapor sorption isotherms of the samples for three adsorption-desorption cycles at varying RH between 0% and 95%. Inverse gas chromatography (IGC) was used to study the surface energy properties of the samples, including dispersive and polar characteristics. The DVS results showed that the EMC was reduced by 30-50% for the TMW samples compared with control samples of unmodified wood (UW) components. A lower reduction was, however, observed for the second and third adsorption cycles compared with that of the first cycle. Ratios between EMC of TMW and that of UW samples were lower for the TMW180 compared with the TMW150 samples, and an overall decrease in such EMC ratios was observed at higher RH for both TMW samples. The IGC results showed that the dispersive contribution to the surface energy was higher at lower surface coverages, ie representing the higher energy sites, for the TMW compared with the UW samples. In addition, an analysis of the acid-base properties indicated a higher KB than KA number, ie a higher basic than acidic contribution to the surface energy, for all the samples. A higher KB number was also observed for the TMW compared with the UW samples, suggested to relate to the presence of ether bonds from increased lignin and/or extractives content at the surface. The KB was lower for TMW180 compared with TMW150, as a result of higher modification temperature of the first, leading to cleavage of these ether bonds.
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17.
  • Lillqvist, Kristiina, et al. (author)
  • THE INFLUENCE OF THERMAL MODIFICATION ON VENEER BOND STRENGTH
  • 2017
  • In: Proceedings of the 13th annual meeting of the Northern European Network for Wood Science and Engineering, September 28-29. ; , s. 56-
  • Conference paper (other academic/artistic)abstract
    • The purpose of this study was to investigate the effect of thermal modification on birchveneer properties relevant in plywood manufacture. The wood material used in thisstudy was a birch (Betula pendula Roth) stem sectioned into small logs nominally 1.2 min length. The logs were completely immersed in a water tank heated to either 70 °C or20 °C. The soaked logs were rotary cut on an industrial scale lathe (Model 3HV66;Raute Oyj, Lahti, Finland) into veneer with a nominal thickness of 0.8 mm.Veneer specimens (150x150 mm2) were cut and thermally modified at 200°C in steamconditions for 2, 4 and 8 h. Mass loss and equilibrium moisture content (EMC) weremeasured after modification. The bond strength of the veneers was measured withautomated bonding evaluation system (ABES- Adhesive Evaluation Systems, Inc.,Corvallis, Oregon, USA) using phenol formaldehyde (PF) resin (Prefere 14J021, PrefereResins Finland Oy, Hamina, Finland). Specimens (20 x 117 mm2), were cut from theconditioned veneer sheets. A liquid PF resin was applied to an area of 5 x 20 mm2 atone end of the veneer specimens (approx. spread rate 100 g m-2). After adhesiveapplication, the veneer-resin assembly was placed into the ABES and after 180 s ofpressing (130 °C and 2.0 MPa) the shear strength of adhesive bond was measured.As expected from previous studies, the mass loss increased and EMC reduced withlonger thermal modification time. No significant difference in mass loss or EMCbetween log soaking temperatures was recorded in this study. The thermal modificationslightly reduced the bond strength; however, longer treatment time did not furtherreduce the bond strength. Therefore, based on this study, thermally modified veneerscould be successfully bonded and
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18.
  • Peñaloza, Diego, et al. (author)
  • Future scenarios for climate mitigation of new construction in Sweden : Effects of different technological pathways
  • 2018
  • In: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526 .- 1879-1786. ; 187, s. 1025-1035
  • Journal article (peer-reviewed)abstract
    • A variety of climate mitigation strategies is available to mitigate climate impacts of buildings. Several studies evaluating the effectiveness of these strategies have been performed at the building stock level, but do not consider the technological change in building material manufacturing. The objective of this study is to evaluate the climate mitigation effects of increasing the use of biobased materials in the construction of new residential dwellings in Sweden under future scenarios related to technological change. A model to estimate the climate impact from Swedish new dwellings has been proposed combining official statistics and life cycle assessment data of seven different dwelling typologies. Eight future scenarios for increased use of harvested wood products are explored under different pathways for changes in the market share of typologies and in energy generation. The results show that an increased use of harvested wood products results in lower climate impacts in all scenarios evaluated, but reductions decrease if the use of low-impact concrete expands more rapidly or under optimistic energy scenarios. Results are highly sensitive to the choice of climate impact metric. The Swedish construction sector can only reach maximum climate change mitigation scenarios if the low-impact building typologies are implemented together and rapidly.
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19.
  • Peñaloza, Diego, 1981- (author)
  • The role of biobased building materials in the climate impacts of construction : Effects of increased use of biobased materials in the Swedish building sector
  • 2017
  • Doctoral thesis (other academic/artistic)abstract
    • A significant share of the global climate change impacts can be attributed to the construction sector. One mitigation strategy is increasing the use of biobased materials. Life cycle assessment (LCA) has been used to demonstrate the benefits of this, but forest complexities create uncertainty due to omission of key aspects. The aim of this thesis is to enhance understanding of the effects of increasing use of biobased materials in climate change mitigation of construction works with a life cycle perspective. Non-traditional LCA methodology aspects were identified and the climate impact effects of increasing the use of biobased materials while accounting for these was studied. The method applied was dynamic LCA combined with forest carbon data under multi-approach scenarios. Diverse case studies (a building, a small road bridge and the Swedish building stock) were used. Most scenarios result in impact reductions from increasing the use of biobased materials in construction. The inclusion of non-traditional aspects affected the results, but not this outcome. Results show that the climate mitigation potential is maximized by simultaneously implementing other strategies (such as increased use of low-impact concrete). Biobased building materials should not be generalised as climate neutral because it depends on case-sensitive factors. Some of these factors depend on the modelling of the forest system (timing of tree growth, spatial level approach, forest land use baseline) or LCA modelling parameters (choice of the time horizon, end-of-life assumptions, service life). To decrease uncertainty, it is recommended to use at least one metric that allows assessment of emissions based on their timing and to use long-term time horizons. Practitioners should clearly state if and how non-traditional aspects are handled, and study several methodological settings. Technological changes should be accounted for when studying long-term climate impacts of building stocks.
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20.
  • Ruponen, J., et al. (author)
  • Tensile-shear strength studies on self-bonded 2-ply birch veneer joint manufactured and tested by applying Automated Bonding Evaluation System (ABES) hot press
  • 2016
  • In: WCTE 2016 - World Conference on Timber Engineering. - : Vienna University of Technology. - 9783903039001
  • Conference paper (peer-reviewed)abstract
    • An Automatic Bond Evaluation System (ABES) hot press was employed to manufacture a self-bonded joint between two veneers of rotary-cut birch (Betula pendula Roth). The hot-pressing conditions were 220 °C and 5.0 MPa, with press times ranging from 180 s to 600 s with 60 s intervals. Additionally, the log-soaking temperature (20 °C and 70 °C) and the veneer initial MC (6% and 11%) were varied to study the effect on the tensile-shear strength of the joints. For one set, the surface properties were altered by acetone extraction. The samples were tested at 11% MC. However, one set was partly duplicated and tested at 6% MC, to study how the testing conditions influenced the bond strength. The maximum average tensile-shear strength was 3.3 MPa, observed after 600 s hot pressing. The studies also included bond-line micromorphology analysis by applying SEM combined with a micromachining surface preparation technique based on UV excimer laser ablation. It was also indicated that longer hot-pressing times, lower veneer initial MC and a lower testing MC resulted in increased tensile-shear strength. Acetone extraction decreased the bond strength with increased standard deviation. Finally, the highest single and average strengths were observed for veneers from higher soaking temperature.
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21.
  • Sedighi Moghaddam, Maziar, et al. (author)
  • Microstructure of chemically modified wood using X-ray computed tomography in relation to wetting properties
  • 2017
  • In: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 71:2, s. 119-128
  • Journal article (peer-reviewed)abstract
    • X-ray computed tomography (XCT) was utilized to visualize and quantify the 2D and 3D microstructure of acetylated southern yellow pine (pine) and maple, as well as furfurylated pine samples. The total porosity and the porosity of different cell types, as well as cell wall thickness and maximum opening of tracheid lumens were evaluated. The wetting properties (swelling and capillary uptake) were related to these microstructural characteristics. The data show significant changes in the wood structure for furfurylated pine sapwood samples, including a change in tracheid shape and filling of tracheids by furan polymer. In contrast, no such changes were noted for the acetylated pine samples at the high resolution of 0.8
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  • Segerholm, Kristoffer, et al. (author)
  • Micromorphology, moisture sorption and mechanical properties of a biocomposite based on acetylated wood particles and cellulose ester
  • 2007
  • In: Wood Material Science and Engineering. - : Informa UK Limited. - 1748-0272 .- 1748-0280. ; 3-4:2, s. 106-117
  • Journal article (peer-reviewed)abstract
    • One of the major issues in a long-term perspective for the use of wood-plastic composites (WPCs) in outdoor applications is the moisture sensitivity of the wood component and the consequent dimensional instability and susceptibility to biological degradation of the composite. In this work, the effects of using an acetylated wood component and a cellulose ester as matrix on the micromorphology, mechanical performance and moisture uptake of injection-moulded WPCs have been studied. Composites based on unmodified and acetylated wood particles, specially designed with a length-to-width ratio of about 5-7, combined with both cellulose acetate propionate (CAP) and polypropylene (PP) matrices were studied. The size and shape of the wood particles were studied before and after the processing using light microscopy, and the micromorphology of the composites was studied using a newly developed surface preparation technique based on ultraviolet laser irradiation combined with low-vacuum scanning electron microscopy (LV-SEM). The water vapour sorption in the composites and the effect of accelerated weathering were measured using thin samples which were allowed to reach equilibrium moisture content (EMC). The length-to-diameter ratio was only slightly decreased for the acetylated particles after compounding and injection moulding, although both the unmodified and the acetylated particles were smaller in size after the processing steps. The tensile strength was about 40% higher for the composite based on acetylated wood than for the composite with unmodified wood using either CAP or PP as matrix, whereas the notched impact strength of the composite based on acetylated wood was about 20% lower than those of the corresponding unmodified composites. The sorption experiments showed that the EMC was 50% lower in the composites with an acetylated wood component than in the composites with an unmodified wood component. The choice of matrix material strongly affected the moisture absorptivity of the WPC. The composites with CAP as matrix gained moisture more rapidly than the composites with PP as matrix. It was also found that accelerated ageing in a Weather-Ometer® significantly increased the moisture sensitivity of the PP-based composites.
  •  
29.
  • Segerholm, Kristoffer, 1979-, et al. (author)
  • Moisture sorption in artificially aged wood-plastic composites
  • 2012
  • In: BioResources. - 1930-2126. ; 7:1, s. 1283-1293
  • Journal article (peer-reviewed)abstract
    • Moisture sorption in wood-plastic composites (WPCs) affects their durability and dimensional stability. In certain outdoor exposures, the moisture properties of WPCs are altered due to e. g. cracks induced by swelling and shrinkage of the components, as well as UV degradation or biological attack. The aim of this work was to study the effect of different artificial ageing routes on the moisture sorption properties of WPCs. Extruded WPCs were prepared with either unmodified or acetylated wood and recycled high-density polyethylene (HDPE). The WPC samples were artificially aged involving water soaking, artificial weathering, and white-or brown-rot decay in different combinations. After the ageing, the samples were conditioned in either 65% or 90% relative humidity (RH) until equilibrium moisture content was reached. A dynamic moisture sorption analyzer was used to monitor the sorption rate of samples subjected to a climate change from 65% to 90% RH. Scanning electron microscopy was used to study the surface morphology of the aged composites. Results showed that the artificial weathering caused cracking of the HDPE matrix at the composite surface, as well as a wood-matrix debonding, resulting in an increased moisture sorption rate. The WPC samples subjected to white-rot decay showed the highest moisture sorption rate.
  •  
30.
  • Segerholm, Kristoffer, 1979-, et al. (author)
  • Mould growth resistance of fungicide-containing WPC
  • 2011
  • In: Proceedings of the 7th meeting of the Nordic-Baltic Network in Wood Material Science & Engineering (WSE). - : Norsk institutt for skog og landskap. ; , s. 25-30
  • Conference paper (peer-reviewed)
  •  
31.
  •  
32.
  • Sjökvist, Tinh, et al. (author)
  • Liquid sorption and swelling behaviour of Norway spruce heartwood and sapwood veneers studied by the multicycle Wilhelmy plate method
  • 2017
  • In: Proceedings of the 13th annual meeting of the Northern European Network for Wood Science and Engineering, September 28-29. ; , s. 140-
  • Conference paper (other academic/artistic)abstract
    • The durability of coated wood in outdoor exposure is strongly influenced by the watersorption and liquid permeability properties of the wood substrate. Those properties mayalso influence the ability of a coating to be absorbed into the substrate. It is known thatthere is a significant difference in the water sorption behaviour between spruce heartandsapwood. However, most studies have been concentrated on wood panels, givingthe average behaviour for the whole panel. This study is using smaller wood samplesgiving a more specific information regarding certain influencing factors. Theinfluencing factors could be, e.g. early- and latewood morphology as well as extractivescontent and composition.The aim of this research is to increase the knowledge about water sorption and swellingproperties of Norway spruce. The objective is to study the water uptake behaviour ofheart- and sapwood veneer samples using a recently developed multicycle Wilhelmyplate method. The method enables to follow the sorption and swelling pattern ofrelatively small wood samples during a number of wetting cycles in water and octane. Italso provides a shorter experimental time compared to tests using larger wood panels.The results in the non-swelling liquid octane indicate that a higher wood porosity resultsin higher liquid permeability for both sap- and heartwood. However, no clear differencein permeability can be observed between the sap- and heartwood samples. The result inpermeability is also valid for measurements in water, although the results are moredifficult to interpret. Moreover, the information from liquid mass uptake of octane andwater gives together an indication of the impact from porosity on the overall liquiduptake of heart- and sapwood.
  •  
33.
  • Sjökvist, Tinh, 1978-, et al. (author)
  • The infuence of heartwood, sapwood and density on moisture fuctuations and crack formations of coated Norway spruce in outdoor exposure
  • 2019
  • In: Journal of Wood Science. - : Springer. - 1435-0211 .- 1611-4663. ; 65:45
  • Journal article (peer-reviewed)abstract
    • The moisture sorption behaviour of wood strongly influences the durability of exterior-coated wood. Wood characteristics are known to influence the water sorption of uncoated wood. Despite this, the majority of the research on coated wood has been focused on the coating properties. This study aims to investigate the impact of heartwood, sapwood and density on the moisture content (MC) and crack formation of coated Norway spruce (Picea abies (L.) Karst.). Boards with film-forming coatings or a non-film-forming coating were exposed outdoors during 3 years. Crack development and the mass of the boards were recorded during this period. Heartwood and sapwood samples showed no differences in MC. Thus, a coating seems to reduce the differences in water sorption behaviour that is present in uncoated heartwood and sapwood spruce. The reduction is probably related to wetting properties and different sorption mechanisms, involving free and bond water diffusion. However, the low-density samples had significantly higher MC levels than the high-density samples. The high-density samples with a non-film-forming coating showed a higher number of cracks than those with lower density. Furthermore, sapwood samples had a remarkably high number of cracks when compared to the corresponding heartwood samples, despite a similar density and MC.
  •  
34.
  •  
35.
  • Sterley, Magdalena, 1959-, et al. (author)
  • Edge and face gluing of green timber using a one-component polyurethane adhesive
  • 2004
  • In: European Journal of Wood and Wood Products. - : Springer Berlin/Heidelberg. - 0018-3768 .- 1436-736X. ; 62:6, s. 479-482
  • Journal article (peer-reviewed)abstract
    • The edge and face gluing of green timber using a one-component polyurethane adhesive was investigated. Knot free and straight grained lamellae of dimensions were prepared for this purpose. The relationship between final shear strength and wood failure percentage after kiln drying of the edge green glued specimens was shown. A slight increase of the shear strength was obtained for specimens tested 24 hour pressing compared with directly pressing.
  •  
36.
  • Tuominen, Mikko, et al. (author)
  • Superamphiphobic overhang structured coating on a biobased material
  • 2016
  • In: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 389, s. 135-143
  • Journal article (peer-reviewed)abstract
    • A superamphiphobic coating on a biobased material shows extreme liquid repellency with static contact angles (CA) greater than 150 degrees and roll-off angles less than 10 degrees against water, ethylene glycol, diiodomethane and olive oil, and a CA for hexadecane greater than 130 degrees. The coating consisting of titanic nanoparticles deposited by liquid flame spray (LFS) and hydrophobized using plasma-polymerized perfluorohexane was applied to a birch hardwood. Scanning electron microscopy (SEM) imaging after sample preparation by UV laser ablation of coated areas revealed that capped structures were formed and this, together with the geometrically homogeneous wood structure, fulfilled the criteria for overhang structures to occur. The coating showed high hydrophobic durability by still being non-wetted after 500 000 water drop impacts, and this is discussed in relation to geometrical factors and wetting forces. The coating was semi-transparent with no significant coloration. A self-cleaning effect was demonstrated with both water and oil droplets. A self-cleanable, durable and highly transparent superamphiphobic coating based on a capped overhang structure has a great potential for commercial feasibility in a variety of applications, here exemplified for a biobased material.
  •  
37.
  • Wang, Tianxiang, 1995-, et al. (author)
  • Adhesively bonded joints between spruce glulam and birch plywood for structural applications : experimental studies by using different adhesives and pressing methods
  • 2023
  • In: Wood Material Science & Engineering. - : Taylor and Francis Ltd.. - 1748-0272 .- 1748-0280. ; 18:3, s. 1141-
  • Journal article (peer-reviewed)abstract
    • Due to the increasing interest in reducing the usage of metals in the construction sector, birch plywood has shown good potential in structural engineering and timber connections as a substitute for the more conventional slotted-in metal plate solutions. However, a proper way of bonding birch plywood with other timber parts that results in adequate connection strength has not been fully investigated. In this paper, experimental studies were carried out to investigate the proper workflow when manufacturing bonded connections made of birch plywood and spruce glulam beams. Tensile shear mechanical tests were then conducted on produced bonded joints to evaluate the bond strength. Three adhesives, i.e. melamine-urea-formaldehyde (MUF), phenol–resorcinol–formaldehyde (PRF), and two-component polyurethane (2C PUR) were evaluated in dry and moist conditions. The influence of three pressing methods, i.e. (a) screw-gluing, (b) clamping by means of clamps, and (c) clamping by application of weight loads, on the bonding strength was investigated. The bonding strength was thereafter compared with the shear strength of spruce glulam and the wood failure percentage was also examined in this study. © 2023 The Author(s). 
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38.
  • Wang, Tianxiang, 1995-, et al. (author)
  • An innovative timber-steel hybrid beam consisting of glulam mechanically reinforced by means of steel rod : Analytical and preliminary numerical investigations
  • 2021
  • In: Journal of Building Engineering. - : Elsevier Ltd. - 2352-7102. ; 43
  • Journal article (peer-reviewed)abstract
    • There is an increasing interest in large-dimensional timber structural elements within the construction sector in order to fulfil the combined demand of sustainability, open spaces and architectural flexibility. Current timber technology allows for efficient production of long-size beams, but many problems are related to their overall high costs due to difficulties in transportation, manufacturing on site and handling during the mounting phase. Hence, the aim of this work is to propose and study an innovative timber-steel hybrid structural element composed of shorter pieces of beams connected and reinforced by means of a system consisting of steel shear keys and steel rods. The small timber elements and steel devices can be prefabricated with low costs and easily assembled into large elements at the construction sites. The proposed system can also be used for retrofitting of existing timber members when it is necessary to increase their strength, stiffness and ductility. The structural behavior of the proposed system was therefore studied both as a connection and as a retrofitting technique, which were analyzed via two types of hybrid beams, one with a splice at mid-span and one without, separately. A simple glulam beam with the same geometrical characteristics of the two hybrid structures was also investigated for the comparison of the structural behavior. The analytical results show that the hybrid beams with and without splice have both obtained significant increasement in the stiffness, strength and ductility. The numerical analyses are limited in the elastic stage due to the elastic mechanical properties assigned to the structural components. The numerical results show good agreement with the analytical ones for each type of beam in terms of the stiffness in the elastic stage. Finally, the influence of the parameters such as the distance between shear keys, slip modulus of shear keys and diameter of rod, on the structural behavior of hybrid beams is discussed in this paper. 
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39.
  •  
40.
  • Wang, Tianxiang, 1995-, et al. (author)
  • Glulam beams adhesively bonded by birch plywood plates in moment-resisting beam-to-beam connections
  • 2024
  • In: Engineering structures. - : Elsevier Ltd. - 0141-0296 .- 1873-7323. ; 302
  • Journal article (peer-reviewed)abstract
    • The design of timber connections is of vital importance in timber structures. Bonded connections exhibit the advantages of lower cost, higher load-bearing capacity, and higher stiffness compared to conventional mechanical connections. However, the potential of the bonded connections has yet to be fully exploited, not only due to their sensitivity to the adhesive types and process-related parameters but also due to the lack of studies regarding the structural performance of the bonded connection in various loading conditions. In this paper, birch plywood plates were utilized to adhesively connect two glulam beam halves to create a longer span. Plywood made of birch was chosen because birch is highly resourced on the Eurasian continent, with its mechanical properties better than most softwoods. Specifically, glulam beams were connected by birch plywood plates at mid-span and then loaded in four-point bending. Four test series with two different bonding areas and birch plywood face grain orientations were carried out. The bonded region was designed as the weakest part to investigate the failure modes, moment capacity, bending stiffness, and moment-rotation angle relationships. Furthermore, numerical models were developed to predict the structural behaviors in the linear elastic stage, while analytical models were proposed and subsequently modified to predict the moment-carrying capacities. Both numerical and analytical models displayed satisfactory agreement with the test results.
  •  
41.
  • Wang, Tianxiang, 1995-, et al. (author)
  • Glulam Frames Adhesively Bonded by Means of Birch Plywood Plates : Preliminary Investigations
  • 2023
  • In: 13th World Conference on Timber Engineering, WCTE 2023. - : World Conference on Timber Engineering (WCTE). ; , s. 1453-1461
  • Conference paper (peer-reviewed)abstract
    • The design of timber connections is of great importance since their performance is decisive for timber structures. The widely adopted technique utilizing the slotted-in steel plates could possibly be replaced by using timber-based gusset plates due to the significant advantages in terms of the environmental impact, economy, ease of prefabrication, and fire resistance of the latter one. Among the timber-based panels, plywood made of birch was chosen in the study due to the combined benefits of the cross laminated configuration of plywood and the superior mechanical properties of birch compared to most softwoods. In this paper, a preliminary experimental investigation was carried out to study the structural performance of the glulam trusses connected by means of bonded birch plywood gusset plates. Tests were performed on ad-hoc designed frame-like specimens. The plywood gusset plates were under-designed to be the weakest link in the structure, so as to study their load-bearing capacity. The knowledge obtained in this study is the first step towards the establishment of a model for the design of truss nodes with bonded plywood gusset plates. In the study, the face grain orientation of birch plywood was varied (0°, 5°, and 15° to the horizontal axis) in three test series. Test results show that the influence of the face grain angle from 0 to 15 degrees on the global stiffness of the frame structure is insignificant and it can be well predicted by a simplified planar 2D numerical models. Two analytical models, namely, the classic so-called 'Whitmore model' along with a more accurate analytical model, were utilized to illustrate the failure mechanism of birch plywood gusset plates with the concept of the effective width and the spreading angle.
  •  
42.
  •  
43.
  • Wang, Tianxiang, 1995-, et al. (author)
  • In-plane mechanical properties of birch plywood
  • 2022
  • In: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 340
  • Journal article (peer-reviewed)abstract
    • There is an increasing demand for engineered wood products in modern structures. Birch plywood is promising in structural applications, due to the combined advantages of its superior mechanical properties and the cross lamination configuration. However, the off-axis mechanical properties of birch plywood have not been thoroughly investigated. The aim of this paper is to establish a comprehensive experimental dataset that could serve as the input in the analytical or numerical models to design birch plywood under various load conditions. Specifically, tensile, compressive and shear tests were conducted under five different angles to the face grain, i.e., from 0 degrees (parallel) to 90 degrees (perpendicular) to the face grain, with an interval of 22.5 degrees. The stress-strain relationships, failure modes, strength and elastic properties of birch plywood are highly dependent on the load-to-face-grain angle. The strength and the elastic properties are also predicted by various analytical and empirical models. Parametric analyses are performed to study the influence of the interaction coefficient F-12 in Tsai-Wu failure criterion and the Poisson's ratio v(xy) in the transformation model on the predicted strength and modulus respectively. Lastly, the possibilities of predicting the on-axis shear modulus based on the off-axis uniaxial tests are discussed in this paper.
  •  
44.
  • Wang, Tianxiang, 1995- (author)
  • In-plane mechanical properties of birch plywood and its performance in adhesively bonded connections
  • 2024
  • Doctoral thesis (other academic/artistic)abstract
    • Birch (Betula spp.) is a hardwood species with a wide natural distribution on the Eurasian continent, especially in northern Europe. Compared with conventional plywood made from softwood, birch plywood has favorable mechanical properties that could be used in new types of efficient connections for timber structures, and thus enable a substitution of current systems using slotted-in steel plates. Such new connections could result in significant advantages in terms of environmental impact and economy as well as ease of prefabrication and assembly. However, birch plywood has rarely been utilized in connections, and therefore, there is a lack of knowledge necessary to design safe timber structures applying such connection systems. In particular, there is a need for increased knowledge of the mechanical properties of birch plywood and its structural performance under various loading conditions. Current connections in timber structures usually also involve mechanical fasteners, e.g., steel screws and dowels, but there is limited use of adhesively bonded (glued) connections. The aim of this thesis is to gain new knowledge required for the development of adhesively bonded connections using birch plywood as gusset plates in structural applications. Examples of such structural applications are timber trusses and portal frames. In this context it is necessary, first, to characterize the in-plane mechanical properties of birch plywood, and second, to investigate its performance in adhesively bonded connections.The results of the mechanical testing show that birch plywood possesses the highest and lowest tensile, compressive, and bending strength and elastic modulus at 0° (parallel) and 45°, respectively, to the face grain (the fiber direction of the face veneers). The opposite findings were noticed for the shear strength and the shear modulus. All these strength values are similar to or higher than the corresponding strength values of common softwood structural timber in its longitudinal direction. Moreover, a size effect on the in-plane bending strength property was observed at 0° and 90° to the face grain but not at other angles, which is attributed to different failure mechanisms. Based on the experimental work, both analytical and numerical models to predict the in-plane mechanical properties of birch plywood are proposed.Three different adhesives systems were used in the studies: melamine-urea-formaldehyde (MUF), phenol-resorcinol-formaldehyde (PRF), and a two-component polyurethane (2C PUR). All adhesives used show adequate bonding strength between birch plywood and spruce glulam. However, the use of the adhesive systems should be further investigated in the future. The different manual pressing methods investigated show no significant influence on the bonding strength. Moreover, the bonding strength changes within a relatively small range when the loading direction is varied from 0° to 90°, which is beneficial for the design of birch plywood in adhesively bonded connections. A clear correlation exists between the bonding strength and the shear strength of the weakest wood adherend.In addition, the moment capacity and bending stiffness of adhesively bonded connections using birch plywood were determined experimentally as well as by analytical and numerical models with a satisfactory agreement.In timber connections, especially those that are prevalently loaded in tension and/or compression (e.g., in timber trusses), the contribution of the plywood width on the load-bearing capacity needs to be quantified. The results show that the tensile strength of birch plywood within the bonded area shows very low angle-dependence. This is possibly due to the restricted crack propagation at 22.5° and 45° when the gap between the bonded regions is small. The tensile capacity of birch plywood loaded at 0°, 22.5°, and 45° reaches a plateau at certain widths of the gusset plate, which can be well predicted and explained by the spreading angle theories proposed in this study.In the future, more studies are required for the further development of the adhesively bonded connections with birch plywood. Some preliminary studies serving this purpose have been presented in the thesis as on-going work.
  •  
45.
  • Wang, Tianxiang, 1995-, et al. (author)
  • Influence of face grain angle, size, and moisture content on the edgewise bending strength and stiffness of birch plywood
  • 2022
  • In: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 223, s. 111227-
  • Journal article (peer-reviewed)abstract
    • Birch plywood exhibits outstanding mechanical properties with regards to tensile, compressive, and shear behaviors, making this engineered wood product promising in timber connection applications. However, the edgewise bending strength and stiffness, which are often critical for the design of gusset plates, have not been investigated thoroughly. Moreover, in engineering applications, the size and moisture content of the plywood plate are in general very different from those adopted in laboratory testing according to current standards. This paper aims to investigate the influence of face grain angle, size, and moisture content on the edgewise bending strength and stiffness of birch plywood. In total, 288 birch plywood specimens were tested in three-point bending at five different face grain angles to the beam longitudinal axis (from 0 degrees (parallel) to 90 degrees (perpendicular), with an angle step of 22.5 degrees), with four different sizes (with the nominal depth of 20 mm, 30 mm, 40 mm, and 50 mm) and three different moisture contents (7.2 %, 11.9 %, and 21.8 %). Analytical and numerical models, both taking non-linear elasto-plastic compressive behaviors into account, were developed for the prediction of the ultimate moment capacity based on different failure definitions. Lastly, the relationships between the bending strength and elastic modulus were analyzed.
  •  
46.
  •  
47.
  • Wang, Tianxiang, 1995- (author)
  • On the in-plane mechanical properties of birch plywood
  • 2022
  • Licentiate thesis (other academic/artistic)abstract
    • Birch plywood has favorable mechanical properties that could be used in new types of connections for timber structures, and thus enable a substitution of the current system with steel plates. Such new connections could result in significant advantages in terms of environmental impact and economy as well as ease of prefabrication and mountability. However, there is a lack of data concerning some of the mechanical properties of birch plywood that would be necessary in order to perform a safe design. In particular, there is a lack of reliable data and understanding of the mechanical properties of birch plywood in directions other than along and perpendicular to the face grain. The aim of this thesis is to gain new knowledge about this anisotropy and to study the variation of the in-plane mechanical properties of birch plywood at different loading angles to the face grain, including effects of size and moisture changes. The goal is that this knowledge will serve as input for the design of birch plywood connections under various loading conditions in timber structures. Specifically, birch plywood specimens were laboratory tested in in-plane tension, compression, shear and bending. The results show that birch plywood possesses the highest tensile, compressive and bending strength and elastic modulus parallel to the face grain and the lowest ones at 45° to the face grain. The opposite findings were noticed for the shear strength and the shear modulus. Moreover, a size effect on the in-plane bending strength property was observed at 0° (parallel) and 90° (perpendicular) to the face grain but not at other angles, which is attributed to the different failure mechanisms. In addition, the increase of moisture leads to the decreased bending strength and elastic modulus in the hygroscopic range. Validated by the experimental work, both analytical and numerical models to predict the mechanical performance of birch plywood under different load conditions and various moisture contents are proposed.
  •  
48.
  • Wang, Tianxiang, 1995-, et al. (author)
  • Prediction of the tensile strength of birch plywood at varying angles to grain
  • 2020
  • In: Proceedings of the 16th Annual Meeting of the Northern European Network for Wood Science and Engineering - WSE2020. ; , s. 80-82
  • Conference paper (other academic/artistic)abstract
    • BackgroundPlywood is one of the earliest produced engineered wood products (EWP). It consists of an uneven number of thin veneers, glued together with the grain direction of adjacent veneers perpendicular to the one another (Sellers 1985). Due to its cross-laminated configuration, plywood exhibits more homogenous mechanical properties than solid wood, making it suitable for versatile connection applications that are subjected to multiple types of stresses in multiple directions. In order to optimise the structural design and analyse the mechanics of the plywood application, the first step is to gain knowledge regarding the mechanical properties of plywood at varying angles to the grain..
  •  
49.
  •  
50.
  • Wang, Tianxiang, 1995-, et al. (author)
  • Spreading angle analysis on the tensile capacities of birch plywood plates in adhesively bonded timber connections
  • 2024
  • In: Engineering structures. - : Elsevier BV. - 0141-0296 .- 1873-7323. ; 315
  • Journal article (peer-reviewed)abstract
    • This paper focuses on a particular application of birch plywood in adhesively bonded connections, namely, a node of a timber truss. The aim is to investigate the influence of the plywood's additional width and the load-to-face grain angles on its load-bearing capacity in tension (tensile capacity). The experimental tests started from the case with the plywood width the same as the glulam width. The reference tensile strengths tested from the specimens with a small gap between glulam elements are high at any load-to-face grain angle, i.e., around 51 MPa, 44 MPa, and 41 MPa at 0°, 22.5°, and 45° to the face grain respectively, due to the changed crack paths of the 22.5° and 45° plywood. The very low angle-dependent tensile strength is unique for cross-grained veneer-based panels in adhesively bonded connections, and is promising for applications in truss nodes. With the increase of the plywood width, the tensile capacity of birch plywood tended to reach a plateau. Test results indicated a low angle-dependence of the maximum tensile capacities of birch plywood but the plateaus were reached at different plywood widths. This phenomenon can be well interpreted by introducing the concept of effective widths and spreading angles. The specific spreading angles were determined by comparing the predicted tensile capacity to the test results, which should be valid for adhesively bonded birch plywood plates in truss nodes irrespective of the geometrical parameters.
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