| 1. |
- Buck, Dietrich, 1990-, et al.
(författare)
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Comparison of Different Assembling Techniques Regarding Cost, Durability, and Ecology - A Survey of Multi-layer Wooden Panel Assembly Load-Bearing Construction Elements
- 2015
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Ingår i: BioResources. - : BioResources. - 1930-2126. ; 10:4, s. 8378-8396
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Tidskriftsartikel (refereegranskat)abstract
- Wood is a pure, sustainable, renewable material. The increasing use of wood for construction can improve its sustainability. There are various techniques to assemble multi-layer wooden panels into prefabricated, load-bearing construction elements. However, comparative market and economy studies are still scarce. In this study, the following assembling techniques were compared: laminating, nailing, stapling, screwing, stress laminating, doweling, dovetailing, and wood welding. The production costs, durability, and ecological considerations were presented. This study was based on reviews of published works and information gathered from 27 leading wood product manufacturing companies in six European countries. The study shows that the various techniques of assembling multi-layer wooden construction panel elements are very different. Cross laminated timber (CLT) exhibited the best results in terms of cost and durability. With regard to ecological concerns, dovetailing is the best. Taking into account both durability and ecological considerations, wooden screw-doweling is the best. These alternatives give manufacturers some freedom of choice regarding the visibility of surfaces and the efficient use of lower-quality timber. CLT is the most cost-effective, is not patented, and is a well-established option on the market today.
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| 2. |
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| 3. |
- Buck, Dietrich, 1990-, et al.
(författare)
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Full-Field Correlated Mechanics of Cross-Laminated Timber
- 2019
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Ingår i: International Digital Image Correlation Society Conference And Workshop (iDICs 2019). - : International Digital Image Correlation Society.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work evaluated the effect of timber quality features on the full-field mechanics of cross-laminated timber (CLT) panels. Panels were individuallysubjected to destructive out-of-plane loading in the principal panel orientation. A digital image correlation (DIC)-based technique was applied fornon-contact full-field measurement and analysis of panel mechanics. The results for 50 layers show that the stiffness of conventional CLT is largelyreduced by the shear resistance of transverse layers. Notably, heterogeneous timber features, such as knots, can reduce the propagation of shear.These results suggest an optimized panel assembly strategy that can be generalized: If shear is dimensioning in an area, e.g. the transverse or thecentral longitudinal layer, the use of knotty timber in that layers can reduce shear propagation. Knots in the compression zone in longitudinal layershave some negative impact, but knots have the largest negative impact in areas of longitudinal layers under tension. Therefore, it is suggested thecurrent grading criteria in the CLT standard be revised to allow the use of more knotty timber in the transverse layers of CLT; doing so could allowa more profitable use of otherwise low-grade timber while producing a stiffer product. The potential of panels constructed according to such anapproach may allow new applications for CLT in timber construction and should be further explored
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| 4. |
- Buck, Dietrich, 1990-, et al.
(författare)
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Impregnation of Wood / End Grain Treatment
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This research presents the findings of a study conducted by Luleå University of Technology (LTU) and Lund University (LTH) on the effect of edge treatment on the end grain of cross-laminated timber (CLT) elements. The objective of the study was to identify whether edge treatment influences the moisture performance and mould risk of CLT.The investigation was conducted through controlled laboratory studies, utilising standardised procedures. Specifically, the end grain of the CLT specimens was exposed to moisture by placing them in contact with a free water surface for 96 hours. Following this exposure, the specimens were dried under controlled conditions. X-ray computed tomography (CT) scanning was used to estimate the moisture content of the specimens and provide detailed spatial information about the moisture distribution within the wood.To further evaluate the effectiveness of edge treatment, the experimental moisture content assessments were compared to values by WUFI simulations. Additionally, annual data for the simulations were conducted using climate data from three different locations: Lund, Stockholm, and Borlänge. These simulations assessed the theoretical impact of edge treatment on mould risk under different climatic conditions.Results revealed that edge treatment has potential to reduce moisture content and mitigate mould risk in CLT elements. Experimentally assessed moisture content values were consistently lower in edge-treated specimens compared to untreated specimens. The calculations and simulations supported these findings, showing a distinct reduction in moisture accumulation and mould risk in edge-treated CLT elements.This study provides insights into the effect of edge treatment on the moisture performance and mould risk in CLT elements. The findings suggest that implementing appropriate edge treatment techniques can enhance the durability of CLT structures, particularly for worksites in regions where climatic conditions fluctuate over the course of construction. Further research and testing are warranted to explore additional factors influencing the effectiveness of edge treatment in CLT applications.
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| 5. |
- Buck, Dietrich, 1990-, et al.
(författare)
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Mechanical Performance of Cross-Laminated Timber Panels with Alternated Layers
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This research assessed the mechanics of cross-laminated timber (CLT) panels with different alternating layer directions. A total of 20 industrially produced panels, configured with 0° longitudinal layers and transverse layers alternating at either ±45° or at 90° were subjected to destructive testing in bending. Four-point bending tests showed higher stiffness and strength for panels with ±45° alternating layers compared with the conventional 90° crosswise configuration. A noncontact numerical cross-correlation full-field measurement technique based on digital image correlation (DIC) was used as the main method of analysis for determining the mechanics in different scales. The results of the DIC analysis showed that the shear strain in bending was a more critical parameter in 90° layers than in adjacent 0° longitudinal layers of conventional configurations. Results infer that the use of CLT panels with ±45° can be beneficial to timber engineering construction and can induce an increase in the use of alternating layer laminates, especially in areas with shear.
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| 6. |
- Buck, Dietrich, 1990-
(författare)
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Mechanics of Cross-Laminated Timber
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increasing awareness of sustainable building materials has led to interest in enhancing the structural performance of engineered wood products. Wood is a sustainable, renewable material, and the increasing use of wood in construction contributes to its sustainability. Multi-layer wooden panels are one type of engineered wood product used in construction.There are various techniques to assemble multi-layer wooden panels into prefabricated, load-bearing construction elements. Assembly techniques considered in the earliest stages of this research work were laminating, nailing, stapling, screwing, stress laminating, doweling, dovetailing, and wood welding. Cross-laminated timber (CLT) was found to offer some advantages over these other techniques. It is cost-effective, not patented, offers freedom of choice regarding the visibility of surfaces, provides the possibility of using different timber quality in the same panel at different points of its thickness, and is the most well-established assembly technique currently used in the industrial market.Building upon that foundational work, the operational capabilities of CLT were further evaluated by creating panels with different layer orientations. The mechanical properties of CLT panels constructed with layers angled in an alternative configuration produced on a modified industrial CLT production line were evaluated. Timber lamellae were adhesively bonded in a single-step press procedure to form CLT panels. Transverse layers were laid at a 45° angle instead of the conventional 90° angle with respect to the longitudinal layers’ 0° angle.Tests were carried out on 40 five-layered CLT panels, each with either a ±45° or a 90° configuration. Half of these panels were evaluated under bending: out-of-plane loading was applied in the principal orientation of the panels via four-point bending. The other twenty were evaluated under compression: an in-plane uniaxial compressive loading was applied in the principal orientation of the panels. Quasi-static loading conditions were used for both in- and out-of-plane testing to determine the extent to which the load-bearing capacity of such panels could be enhanced under the current load case. Modified CLT showed higher stiffness, strength, and fifth-percentile characteristics, values that indicate the load-bearing capacity of these panels as a construction material. Failure modes under in- and out-of-plane loading for each panel type were also assessed.Data from out-of-plane loading were further analysed. A non-contact full-field measurement and analysis technique based on digital image correlation (DIC) was utilised for analysis at global and local scales. DIC evaluation of 100 CLT layers showed that a considerable part of the stiffness of conventional CLT is reduced by the shear resistance of its transverse layers. The presence of heterogeneous features, such as knots, has the desirable effect of reducing the propagation of shear fraction along the layers. These results call into question the current grading criteria in the CLT standard. It is suggested that the lower timber grading limit be adjusted for increased value-yield.The overall experimental results suggest the use of CLT panels with a ±45°-layered configuration for construction. They also motivate the use of alternatively angled layered panels for more construction design freedom, especially in areas that demand shear resistance. In addition, the design possibility that such 45°-configured CLT can carry a given load while using less material than conventional CLT suggests the potential to use such panels in a wider range of structural applications. The results of test production revealed that 45°-configured CLT can be industrially produced without using more material than is required for construction of conventional 90°-configured panels. Based on these results, CLT should be further explored as a suitable product for use in more wooden-panel construction.
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| 7. |
- Buck, Dietrich, 1990-, et al.
(författare)
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Mechanics of diagonally layered cross-laminated timber
- 2018
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Ingår i: WCTE 2018 - World Conference on Timber Engineering. - : World Conference on Timber Engineering (WCTE).
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Konferensbidrag (refereegranskat)abstract
- This research evaluated the mechanics of cross-laminated timber (CLT) panels with different layer orientations. A total of 20 industrially produced panels, configured with 0° longitudinal layers and transverse layers alternating at either ±45° or the conventional 90°, were tested. Each panel was subjected to destructive out-of-plane testing in the principal panel orientation to evaluate stiffness and strength in bending. Four-point bending tests showed higher stiffness and strength for panels with ±45° alternating layers compared to 90°. A non-contact full-field measurement and analysis technique based on digital image correlation (DIC) was utilised for the main mechanical analysis at different scales. DIC evaluations of 100 CLT panel layers showed that a considerable part of the stiffness of conventional CLT is reduced by the shear resistance of transverse layers. Heterogeneous wooden features, such as knots, reduce the propagation of shear fraction along the layers. These results call into question the present grading criteria in the CLT standard: It is suggested that the current lower grading limit be adjusted for increased value-yield. The overall experimental results suggest the use of CLT panels with a ±45° layered configuration would be beneficial for timber engineering construction. They also motivate the use of alternatively angled layered laminates in design and construction, especially in areas subjected to shear. Based on these results, CLT should be further explored as a suitable product to potentially facilitate the use of wooden panels in more construction applications.
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| 8. |
- Buck, Dietrich, 1990-, et al.
(författare)
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Moisture- and mould-resistance: multi-modal modelling leveraging X-ray tomography in edge-sealed cross-laminated timber
- 2023
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 230
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Tidskriftsartikel (refereegranskat)abstract
- Edge-sealing, which involves treating the edges of wood products, improves water resistance. This study investigated the feasibility of edge-sealed cross-laminated timber (CLT) panels to reduce capillary water uptake, thereby resisting mould formation. The water and vapour permeabilities of ten characteristically different single-layer sealant coating systems were systematically determined. Multi-modal assessment leveraged by computed tomography (CT) scanning methodology was used to enhance detection of material characteristics beyond the standard coating permeability assessment. Moisture content was observed to change during the specimens’ absorption and desorption depending on the sealant system applied. The results revealed different characteristics of coatings during the water absorption and desorption stages. Findings from this study were used to develop recommendations regarding the water resistance of coating systems, curing time, susceptibility to mould formation, and industrial applicability. Results suggest that edge-sealed CLT could minimise the risk of mould formation, which can occur at worksites with minimal weather protection. The method developed in this study provides a basis to evaluate new coating systems and determine which use case is the best for a particular coating type. This study also incorporates insights from industry to identify future research orientations, which may pave the way for new designs and assessment techniques.
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| 9. |
- Buck, Dietrich, 1990-, et al.
(författare)
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Multivariate Image Analysis Applied to Cross-Laminated Timber: Combined Hyperspectral Near-Infrared and X-ray Computed Tomography
- 2023
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Ingår i: Journal of Spectroscopy. - : Hindawi Publishing Corporation. - 2314-4920 .- 2314-4939.
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Tidskriftsartikel (refereegranskat)abstract
- Engineered wood products, such as cross-laminated timber (CLT), are becoming more popular in the designs of modern sustainable buildings. This increased production of CLT requires more robust, yet less labour-intensive means to assess the material characteristics of whole CLT panels. In exploring ways of improving efficiency, this study explores multivariate image analysis (MIA) via partial least squares discriminant analysis (PLS-DA) machine learning as a means to classify CLT material features. CLT panels underwent nondestructive testing using near-infrared (NIR) hyperspectral imaging and X-ray computed tomography (CT) analysis. MIA was performed on these results to build predictive models for wood features, such as fibre alignment and knot type. The models showed that it was possible to classify material features on the surface of CLT using NIR alone; whilst when combined with X-ray data, it enhanced the predictive ability of material features throughout the CLT volume. These first results from such modelling have the potential to help map the chemical and physical material properties of CLT, improving the manufacturing efficiency of the product and allowing greater sustainability of engineered wood products.
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| 10. |
- Buck, Dietrich, 1990-, et al.
(författare)
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Production and In-Plane Compression Mechanics of Alternatively Angled Layered Cross-Laminated Timber
- 2018
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Ingår i: BioResources. - : University of North Carolina Press. - 1930-2126. ; 13:2, s. 4029-4045
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Tidskriftsartikel (refereegranskat)abstract
- Increasing awareness of sustainable building materials has led to interest in enhancing the structural performance of engineered wood products. This paper reports mechanical properties of cross-laminated timber (CLT) panels constructed with layers angled in an alternative configuration on a modified industrial CLT production line. Timber lamellae were adhesively bonded together in a single-step press procedure to form CLT panels. Transverse layers were laid at an angle of 45°, instead of the conventional 90° angle with respect to the longitudinal layers’ 0° angle. Tests were carried out on 20 five-layered CLT panels divided into two matched groups with either a 45° or a 90° configuration; an in-plane uniaxial compressive loading was applied in the principal orientation of the panels. These tests showed that the 45°-configured panels had a 30% higher compression stiffness and a 15% higher compression strength than the 90° configuration. The results also revealed that the 45°-configured CLT can be industrially produced without using more material than is required for conventional CLT 90° panels. In addition, the design possibility that the 45°-configured CLT can carry a given load while using less material also suggests that it is possible to use CLT in a wider range of structural applications.
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