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Strength grading of sawn timber in Europe: an explanation for engineers and researchers

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Abstract

This paper is a concise explanation of the normative background to strength grading in Europe, addressing important aspects that are commonly misunderstood by structural engineers and timber researchers. It also highlights changes that are being made to the standards to: incorporate requirements of the construction products regulations; add improvements to the system to accommodate the latest knowledge and technology; and widen the application of the standards. Where designs need to be optimised, there is an opportunity to use the system more intelligently, in combination with the latest technology, to better fit design values to the true properties of the timber resource. This can bring a design enhancement equivalent to effort improving other aspects of the structure, such as connectors and reinforcement. Parallel to this, researchers working on other aspects of structural improvement need to understand what grades really mean in respect of the properties of the timber, in order to correctly analyse the results of testing. It is also useful to know how techniques used in grading can assist with material properties characterisation for research. The amount of destructive testing involved in establishing machine grading settings and visual grading assignments presents a barrier to greater use of local timber, and diversification of commercial species, so it is important that any researcher assessing the properties of such species should consider, from the outset, doing the research in a way that can contribute to a grading dataset at a later date. This paper provides an overview of what is required for this.

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References

  • Baltrušaitis A, Pranckevičienė V (2012) Density and stiffness-strength variations within Lithuanian-grown Scots pine trees. Proceedings of COST action FP1004 meeting “enhance mechanical properties of timber, engineered wood products and timber structures”, 19–20 April 2012, Zagreb, Croatia. University of Bath. ISBN 85790 176 2

  • Brunetti M, Nocetti M, Burato P (2013) Strength properties of chestnut structural timber with wane. Adv Mater Res 778:377–384

    Google Scholar 

  • Conde M, Fernández-Golfín JI, Hermoso E (2007) Improving the prediction of strength and rigidity of structural timber by combining ultrasound techniques with visual grading parameters. Mater Construcc 57(288):49–59

    Google Scholar 

  • Denzler JK, Glos P (2008) Size effects in bending, CIB W18, proceedings paper 41-5-1. St. Andrews, Canada

  • Denzler JK, Linsenmann P (2014) Utilization of microwave measurement in timber strength grading. Proceedings of COST action FP1004 meeting “experimental research with timber”, 21–23 May 2014, Czech Technical University in Prague. University of Bath. ISBN 1 85790 183 5

  • Deublein M, Mauritz R, Köhler J (2010) Real-time quality Evaluation of structural timber. Proceedings of 11th world conference on timber engineering, WCTE2010, 20-24 June 2010, Riva del Garda, Italy

  • Guaita M, Baño V (2012) F.E.M. analysis of the strength loss in timber beams of Pinus sylvestris due to the presence of circular knots. Proceedings of COST action FP1004 meeting “enhance mechanical properties of timber, engineered wood products and timber structures”, 19–20 April 2012, Zagreb, Croatia. University of Bath. ISBN 85790 176 2

  • Moore JR, Lyon AJ, Searles GJ, Lehneke SA, Ridley-Ellis DJ (2013) Within- and between-stand variation in selected properties of Sitka spruce sawn timber in the UK: implications for segregation and grade recovery. Ann For Sci 70(4):403–415

    Google Scholar 

  • Olsson A, Oscarsson J, Serrano E, Källsner B, Johansson M, Enquist B (2013) Prediction of timber bending strength and in-member cross-sectional stiffness variation on the basis of local wood fibre orientation. Eur J Wood Wood Prod 71(3):319–333

    CAS  Google Scholar 

  • Piter JC (2012) Size effect on bending strength in sawn timber of fast-growing Argentinean Eucalyptus grandis. Analysis according to the criterion of European standards. Eur J Wood Prod 70:17–24

    Google Scholar 

  • Rais A, Pretzsch H, van de Kuilen J-WG (2014) Roundwood pre-grading with longitudinal acoustic waves for production of structural boards. Eur J Wood Prod 72:87–98

    Google Scholar 

  • Ranta-Maunus A (2012) Determination of settings in combined strength, stiffness and density grading of timber. Eur. Wood Prod 70:883–891

    Google Scholar 

  • Ranta-Maunus A, Denzler JK, Stapel P (2011) Strength of European timber. Part 2. Properties of spruce and pine tested in Gradewood project. VTT Technical Research Centre of Finland. ISBN: 978-951-38-7521-3. 115

  • Ravenshorst GJP, van de Kuilen J-WG (2016) A new approach for the derivation of settings for machine graded timber. Wood Mat Sci Eng 11(2):79–94

    Google Scholar 

  • Ridley-Ellis D (2014) Derivation of MTG 960, mtgBATCH 962 and mtgBATCH 966 grading machine settings for UK larch, TC124/WG2/TG1 approved grading report TG1/201410/32

  • Rouger F (2014) Letter sent to SG18 members about application of clause 6.2 of EN 14081-3, convenor of CEN TC124/WG2, 28th October 2014, document number N 1296

  • Sandomeer MK, Kohler J, Faber MH (2008) Adaptive adjustment of grading machine settings. Proceedings of the COST E53 conference in Delft, Netherlands, 29–30 October. Delft University of Technology. ISBN/EAN: 978-90-5638-202-5

  • Stapel P, van de Kuilen J-WG (2013) Effects of grading procedures on the scatter of characteristic values of European grown sawn timber. Mater Struct 46(9):1587–1598

    Google Scholar 

  • Stapel P, van de Kuilen J-WG (2014) Efficiency of visual strength grading of timber with respect to origin, species, cross section, and grading rules: a critical evaluation of the common standards. Holzforschung 68(2):203–216

    CAS  Google Scholar 

  • Steffen A, Johansson CJ, Wormuth EW (1997) Study of the relationship between flatwise and edgewise moduli of elasticity of sawn timber as a means to improve mechanical strength grading technology. Holz Roh- Werkst 55(2):245–253

    Google Scholar 

  • TG1 (2012) Guidelines for sampling a growth area for deriving machine settings. 6th draft 18 October 2012. CEN TC123/WG2/TG1

  • TG1 (2014) TG1 Decisions. 5th March 2014. CEN TC123/WG2/TG1

  • Vega A, Dieste A, Guaita M, Majada J, Baño V (2012) Modelling of the mechanical properties of Castanea sativa Mill. structural timber by a combination of non-destructive variables and visual grading parameters. Eur J Wood Prod 70(6):839–844

    Google Scholar 

  • Vega A, Arriaga F, Guaita M, Baño V (2013) Proposal for visual grading criteria of structural timber of sweet chestnut from Spain. Eur J Wood Prod 71:529–532

    CAS  Google Scholar 

  • Yaitskova N (2014) Time-of-flight of transversal ultrasonic scan of wood: modeling versus measurement. Proceedings of COST action FP1004 meeting “experimental research with timber”, 21–23 May 2014, Czech Technical University in Prague. University of Bath. ISBN 1 85790 183 5

  • Ziethén R (2008) Reliability of proof-loaded Norway spruce. Holz Roh Werkst 66:401–408

    Google Scholar 

Standards

  • BS 4978:2007+A1:2011 (2011) Visual strength grading of softwood—specification. British Standards Institution, London

    Google Scholar 

  • DIN 4074-1:2012 (2012) Strength grading of wood—part 1: Coniferous sawn timber. German Institute for Standardization, Berlin

    Google Scholar 

  • DIN 4074-1:2012 (2013) Visual grading for structural sawn timber—Coniferous timber. Spanish Association for Standardisation and Certification, Madrid

    Google Scholar 

  • UNE 56546:2013 (2013) Visual grading for structural sawn timber–Hardwood timber. Spanish Association for Standardisation and Certification, Madrid

    Google Scholar 

  • EN 338:2009 (2009) Structural timber—strength classes. European Committee for Standardization, Brussels

    Google Scholar 

  • FprEN 338:2015 (2015) Structural timber—strength classes, European Committee for Standardization, Brussels

  • EN 384:2010 (2010) Structural timber—determination of characteristic values of mechanical properties and density. European Committee for Standardization, Brussels

    Google Scholar 

  • FprEN 384:2015 (2015) Structural timber—determination of characteristic values of mechanical properties and density. European Committee for Standardization, Brussels

    Google Scholar 

  • EN 408:2010+A1:2012 (2012) Timber structures – Structural timber and glued laminated timber—determination of some physical and mechanical properties. European Committee for Standardization, Brussels

    Google Scholar 

  • EN 1912:2012 (2013) Structural timber—strength classes—assignment of visual grades and species, incorporating corrigendum August 2013. European Committee for Standardization, Brussels

    Google Scholar 

  • EN 1990:2002+A1:2005 (2010) Eurocode—basis of structural design (Incorporating corrigenda December 2008 and April 2010). European Committee for Standardization, Brussels

    Google Scholar 

  • EN 1995-1-1:2004+A2:2014 (2014) Eurocode 5: design of timber structures—part 1-1: general—common rules and rules for buildings. European Committee for Standardization, Brussels

    Google Scholar 

  • EN 14081-1:2005+A1:2011 (2011) Timber structures—strength graded structural timber with rectangular cross section—part 1: general requirements. European Committee for Standardization, Brussels

    Google Scholar 

  • FprEN 14081-1:2015 (2015) Timber structures—strength graded structural timber with rectangular cross section—part 1: general requirements. European Committee for Standardization, Brussels

    Google Scholar 

  • EN 14081-2:2010+A1:2012 (2012) Timber structures—strength graded structural timber with rectangular cross section—part 2: machine grading; additional requirements for initial type testing. European Committee for Standardization, Brussels

    Google Scholar 

  • EN 14081-3:2012 (2012) Timber structures—strength graded structural timber with rectangular cross section—part 3: machine grading; additional requirements for factory production control. European Committee for Standardization, Brussels

    Google Scholar 

  • FprEN 16737:2015 (2015) Structural timber—visual strength grading of tropical hardwood. European Committee for Standardization, Brussels

    Google Scholar 

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Acknowledgments

The authors are grateful to COST Action FP1004 “Enhance mechanical properties of timber, engineered wood products and timber structures” for enabling this collaboration.

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Authors and Affiliations

  1. Centre for Wood Science and Technology, Edinburgh Napier University, 10 Colinton Road, Edinburgh, EH10 5DT, UK

    Dan Ridley-Ellis

  2. Holzforschung München, Technische Universität München, Winzererstr. 45, 80797, Munich, Germany

    Peter Stapel

  3. Institute of Structures and Transport, Universidad de la República, Julio Herrera y Reissig 565, 11300, Montevideo, Uruguay

    Vanesa Baño

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  1. Dan Ridley-Ellis
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  3. Vanesa Baño
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Correspondence to Dan Ridley-Ellis.

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Ridley-Ellis, D., Stapel, P. & Baño, V. Strength grading of sawn timber in Europe: an explanation for engineers and researchers. Eur. J. Wood Prod. 74, 291–306 (2016). https://doi.org/10.1007/s00107-016-1034-1

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