| 1. |
- Blomqvist, Lars, 1962-, et al.
(författare)
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EXPERIMENTAL AND NUMERICAL ANALYSES OF A CONNECTION FOR CLT STRUCTURES
- 2023
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Ingår i: Proceedings of the 2023 World Conference on Timber Engineering (WCTE). - Oslo, Norway : Curran Associates, Inc.. ; , s. 1154-1159
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Konferensbidrag (refereegranskat)abstract
- Although building systems made of cross-laminated timber (CLT) have become common in Sweden in the past 20 years and they have developed rapidly during the same period, steps remain to be taken to simplify the assembly of such systems, especially at construction sites. Current construction methods, however, remain labour-intensive and thus show room for improvement.This paper describes a novel connection for the assembly of building elements made of CLT. Simple and inexpensive, the connection is fairly insensitive to manufacturing tolerances and enables rapid, more efficient construction than the connections for CLT structures currently used. Test results show the excellent strength and stiffness of the connection, which also allows the replacement of numerous fasteners, including nails and screws, with only a single steel rod.
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| 2. |
- Blomqvist, Lars, 1962-, et al.
(författare)
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Stress distribution in veneers under lamination and simultaneously bending : an experimental and numerical investigation
- 2023
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis Group. - 1748-0272 .- 1748-0280. ; 18:3, s. 995-1002
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Tidskriftsartikel (refereegranskat)abstract
- Laminated veneer products (LVPs) are veneers glued together into a predetermined shape. Experimental and numerical investigations were performed under lamination and simultaneously bending of veneer laminate to study the stress distribution in the laminate. Laminates of different thicknesses were made of peeled veneers of European beech. The veneers were coated with adhesive, inserted in a mould which had the shape of a semicircle, and finally pressed at 20 degrees C to a laminate. Two Teflon-polymer films including sensors for measurement of the contact pressure were placed on both sides of the laminate to measure the local contact pressure (contact stress) between the laminate and the mould. At the beginning of the bending process, the contact stresses were locally distributed over the laminate in a similar pattern as in a three-point bending; after the laminate was further bent, the stress distribution rearranged to be as in four-point bending. In the end of the moulding, the local contact stresses increased over the entire laminate and reached a 'peak-value' over bent area in the middle part of the mould. A finite-element model was created to study the bending process. Regarding the overall development of the contact stress variations, the experimental and the numerical results agreed.
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| 3. |
- Brandon, Daniel, et al.
(författare)
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High-Fire-Resistance Glulam Connections for Tall Timber Buildings
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Tall timber buildings generally require fire resistance ratings of 90 minutes, 120 minutes or more. The vast majority of fire tested structural timber connections, however, did not reach a fire resistance that was relevant for these buildings. Commonly timber connections between glued laminated timber members comprise of exposed steel fasteners, such as bolts, screws, nails and dowels. However, it has previously been concluded that connections with exposed steel fasteners, generally do not achieve fire resistance ratings of 30 minutes and are, therefore, inadequate to be implemented in tall timber buildings without fire encapsulation. The research project presented in this report consists of four connection fire tests that are designed to achieve structural fire resistance ratings of 90 minutes, using different design strategies. This goal was achieved for all tested column-beam connections. A single test of a moment resisting connection did not lead to a fire resistance rating of 90 minutes, due to timber failure at the smallest cross-section after 86 minutes. The low temperature of the steel fasteners and the limited rotation of the connection, however, suggest that the connection would have been capable of achieving a 90 minutes fire resistance rating if larger beam cross-sections would be used.
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| 4. |
- Jockwer, Robert, 1984, et al.
(författare)
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FATIGUE RESISTANCE OF ADHESIVE BONDED CONNECTIONS WITH AND WITHOUT INTERNAL STEEL PLATES IN LARGE TIMBER STRUCTURES
- 2023
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Ingår i: World Conference on Timber Engineering (WCTE 2023). ; 4, s. 2118-2124
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Konferensbidrag (refereegranskat)abstract
- A modular wooden wind turbine tower has been developed by the Swedish company Modvion AB, where the prefabricated modular elements are connected by glued timber-timber edge joints and by hybrid timber joints with bonded-in perforated steel plates. The application of wood-based products in such a demanding application and highperformance structure is challenging and a variety of questions had to be solved to ensure a reliable performance. The fatigue performance of the adhesive bonded connections has been evaluated in a research project and is presented in this paper. Test specimens of the fatigue resistance of the adhesive and the bond line has been developed. Different stress ratios with alternating loads and high numbers of load cycles have been tested. The results of the tests are presented in this paper.
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| 5. |
- Johansson, Carl-Johan, et al.
(författare)
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Sågverksnytt nr 1
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)
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| 6. |
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| 7. |
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| 8. |
- Lycken, Anders, et al.
(författare)
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Development of a simulation-evaluation program for introducing and using output control in the sawmill industry
- 2010
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Ingår i: Proceedings of the final conference of COST Action E53. - : Edinburgh Napier University.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A computer program for simulating output control has been developed. The calculations in the program follow the standard EN 14081-3:2005, where output control is described. The purpose of the simulator is to make it possible to improve the yield without jeopardizing the safety of the produced boards by testing different approaches in grading. The program is a research tool, as well as a program to use in production where output control is used. In the program is it possible to test e.g. the influence of change of IP-values, number of grades, pre-grading of logs, raw material region, etc. The result of a simulation is shown both as diagrams and numeral. The standard C-grades are pre-programmed with K-, Y- and Z-coefficients according to the standard. Other grades can be added by the user.
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| 9. |
- Lycken, Anders, et al.
(författare)
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State of the art summary on industrialstrength grading, including standards
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report is a state-of-the-art summary on industrial strength grading of wood. Some used methods for grading of wood, both logs and boards, are presented, as well as some new concepts. European standards for strength grading of wood are presented, as well as some national standards and regulations for Austria, Germany and Sweden.
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| 10. |
- Lycken, Anders, et al.
(författare)
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Summary of industrial view on strengthgrading based on interviews
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents the industrial view regarding strength grading, based on interviews with personnel of sawmills and manufacturers of grading systems. The sawmills are Swedish, German and Austrian enterprises, while the manufacturers are from Sweden, Finland, Germany and Italy. The interviews were performed during 2019 and 2020.In the last two decades, knowledge has been accumulated with respect to raw material characterisation of wood, from the standing tree to the end product.It is known that log pre-grading has the potential to significantly improve raw material utilisation, because at that stage of production one is still free to choose the cutting pattern(sawn product dimensions). 3D-log scanning immediately before sawing allows improving log rotation and positioning for cutting optimisation to maximise volume yield, which is already widely used in sawmills.One of the major technological breakthroughs of the last years is the development of industrial computed tomography log scanning, which provides a much more detailed insight into each individual log than 3D outer shape log scanning and discrete X-rayscanning.Three new approaches to strength grading is presented: pure log grading; integrated grading, where log information is used to improve the precision; sequential strengthgrading, where log pre-grading is followed by board grading.The interviews show that the use of automatic strength grading is different between the countries. In Sweden all mills use some automatic grading system, while German mills rely to a large extend on visual grading.The answers show that the interviewed industrial persons in general have knowledge about the capabilities of log sorting and grading with 3-D, discrete X-ray and computer tomography, CT. The knowledge about acoustic log scanning is not as good as for the other techniques.The interviewed sawmillers had in general a strong sense that log tomography could improve the yield, both in volume and value, from the logs. But in contrast to that, the Swedish sawmillers were confident in that CT is a significant improvement over the other scanning techniques. The German sawmillers did not have the same confidence in the CT-scanning´s possibilities. Only few of the Swedish and the German sawmillers saw any large potential in adding acoustic scanning to the other log scanning techniques.The large Austrian enterprises were mainly interested in the possibilities, the advantagesand disadvantages of the new technology of industrial computed tomographyfor round timber. For the other Austrian companies, the focus was on less cost intensive systems such as scanners for determining the dynamic modulus of elasticity, logouter shape or grain deviations.The most important features for grading are knots, their position, status and size. Alsorot and top rupture are important to be able to make a good grading of the log. A more“fuzzy” grading is also wanted, meaning that the rules shall not be too strict.The manufacturers in general said that normal development is ongoing. Larger, revolutionary, inventions will not be presented in this manner.
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| 11. |
- Weidenhiller, A., et al.
(författare)
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Improved strength grading based on log and board measurements - Review and outlook : The research project READistrength
- 2021
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Ingår i: World Conference on Timber Engineering 2021, WCTE 2021. - : World Conference on Timber Engineering (WCTE).
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Konferensbidrag (refereegranskat)abstract
- Timber utilisation and wood construction are fundamental components of Europe's strategy on progressing towards a sustainable bio-based economy. Both components require optimised strength grading procedures in Europe's sawmills. To further improve the current procedures, quality assessment and segregation of the raw material need to start already at the roundwood stage. Furthermore, the quality information should be made accessible throughout the production process to leverage the full potential for optimisation. This paper discusses the current state of research on combined log and board strength grading with a focus on the situation in Europe. It highlights limitations due to technology and current standardisation and identifies knowledge gaps and research opportunities. The European research project READiStrength (resource-efficient and data-driven integrated log and board strength grading) has been initiated to address these issues.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Ziethén, Rune
(författare)
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ICT and the Wood Industry
- 2005
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Ingår i: Information Technology and the Forest Sector. - Vienna : IUFRO. - 3901347569
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 19. |
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| 20. |
- Ziethén, Rune, et al.
(författare)
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Kebony - an Alternative to Teak for Boat Decking
- 2009
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Ingår i: Proceedings of The Fourth European Conference on Wood Modification.. - : SP Technical Research Institute of Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 21. |
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| 22. |
- Ziethén, Rune, et al.
(författare)
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Machine strength grading – “output control” as a method for production control
- 2010
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Ingår i: Proceedings of the 11<sup>th</sup> World Conference on Timber Engineering, WCTE 2010, June 20-24, Riva del Garda, Italy.
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Konferensbidrag (refereegranskat)abstract
- The paper describes the Output control method in EN 14081-3 as an alternative to the more common machine control method in EN 14081-2 for strength grading of timber. A newly developed program for analysing settings and varying input material is presented, as well as results from the analysis. If output control is used instead of machine control, it is possible to increase the yield, at the expense of making more proof-loading tests. The output control method can hardly catch a shift in input material quality, unless the shift stretches over several weeks. At present is the evaluation of the proof-loading results for MOR and MOE dependant of each other. If one of the properties goes out of control then both properties are evaluated according to the out-of-control procedure. This results in an inconsistent evaluation of the grading result. A pre-grading of logs gives a more reliable grading but results also in a lower yield.
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| 23. |
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| 24. |
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| 25. |
- Ziethén, Rune, et al.
(författare)
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Machine strength grading - prediction limits - evaluation of a new method for derivation of settings
- 2010
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Ingår i: Proceedings of the 11th World conference of timber engineering. WCTE2010, June 20-24, Riva del Garda, Italy..
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Konferensbidrag (refereegranskat)abstract
- This paper presents and analyses a new method for derivation of setting values for strength grading machines. The method uses a model for the relationship between indicating property (measured by a grading machine, IP) and the grade determining property (GDP). This model is of course not perfect and by summarising the errors in the model a confidence interval for the model can be calculated. The confidence interval is used for creating a prediction interval. The lower limit of the prediction interval, the prediction limit, is used to predict the GDP. The prediction limit method is analysed and evaluated by well defined input data. It is shown that fewer perimental data than required by the method in EN 14081-2 today is needed to determine reliable settings but the producer is awarded with less conservative settings with an increased number of experimental data. A weak correlation between IP and GDP or a high coefficient of variation also results in conservative settings. The settings are not dependent on average strength of the raw material used for deriving the settings.
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| 26. |
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| 27. |
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| 28. |
- Ziethén, Rune, et al.
(författare)
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Non-destructive test technique based on resonant vibrations - Application on Wood-Based Panels. Nordtest project no. 1487-00
- 2002
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Rapport (refereegranskat)abstract
- In the European production control standard for wood based panels, EN 326-2, there is an opportunity to use alternative test procedures. To find efficient test procedures which reduce the control costs in terms of destructed material and man efforts is an important task. One technique regarded as possible to use is based on measurements of resonant vibrations. The method is already accepted for grading of structural timber. For wood based panels there is a need not only to determine the strength and stiffness in the plane of the panels but also to determine the inter-nal bond. The objective of this project was to investigate the potential of using resonant vi-brations as an alternative test procedure for whole panels. The approach was to examine if there is a correlation between resonant vibrations on whole panels and mechanical properties, determined according to the EN-standards. Both axial and flexural vibrations were studied. For flexural vibration it was necessary to treat the results to be able to find a resonant flexural frequency in the noise. The results from the project show that the correlation between dynamic MOE and bending properties is better for panels than for solid wood. The dynamic MOE is, however, not suitable for predicting the bending properties for one single panel type with a small range in MOE or bending strength. The damping was very weakly correlated both to the bending properties and to the internal bond. The internal bond was also weakly correlated to the resonant frequencies. Based on these results, resonant vibrations do not seem to be an alternative to destructive testing without further developments. The technique may, however, have a poten-tial to be used as a control tool in the production line. The correlations are proba-bly strong enough to display the mean value and trends of the bending properties during a certain time of production.
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| 29. |
- Ziethén, Rune
(författare)
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Reliability of proof-loaded Norway spruce
- 2008
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Ingår i: European Journal of Wood and Wood Products. - 0018-3768 .- 1436-736X. ; 66:6, s. 401-408
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Tidskriftsartikel (refereegranskat)
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| 30. |
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| 31. |
- Östmark, Emma, et al.
(författare)
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Bio-resin Bonded Acetylated OSB
- 2009
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Ingår i: Proceedings of The Fourth European Conference on Wood Modification.. - : SP Technical Research Institute of Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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