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Dr John Moore 22 November 2007

Dr John Moore 22 November 2007. Growing Trees for the Future of Construction. Resource Characterisation. How do site, silviculture and genetics affect the properties of structural timber?. Presentation Overview. Definition of key wood properties Sources and extent of variation

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Dr John Moore 22 November 2007

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  1. Dr John Moore22 November 2007 Growing Trees for the Future of Construction

  2. Resource Characterisation How do site, silviculture and genetics affect the properties of structural timber?

  3. Presentation Overview • Definition of key wood properties • Sources and extent of variation • Benchmarking the Sitka spruce resource

  4. Key Wood Properties • Wood properties of interest depend on the intended end use • Key wood properties for construction – “3 S’s” • Modulus of Elasticity (stiffness) • Modulus of Rupture (strength) • Dimensional stability

  5. Timber Strength Classes – EN338

  6. Mechanical properties affected by: Wood density Microfibril angle Knots These in turn are affected by: Genetics Environment (soils and climate) Silviculture (i.e., spacing, thinning, pruning) Rotation length Factors Affecting Timber Properties

  7. Variation Occurs at Different Scales • Large scale variation between sites • Soil type • Climate (temperature, rainfall) • Variation within a stand • Microsite effects • Genetic differences between trees

  8. Variation within a Tree (Diagram Courtesy of Jonathon Harrington)

  9. Studying Timber Properties Every piece of timber is linked to a log, tree and stand Battens & Small clears Discs Radial Slices Logs Tree –

  10. Tree and Log Assessment Dynamic MOE predicted from measurements of acoustic velocity made on standing trees and logs (Photos courtesy of Alexis Achim)

  11. Studying Timber Properties

  12. Measurement of Timber Properties Four-point bending test with Zwick Z050 Measurement of batten shape using FRITS frame

  13. Distribution of Mechanical Properties

  14. Sources of Variation in MOE • Rep 5.2% • Plot within rep 0.6% • Tree within plot 38.4% • Log within tree 5.3% • Batten within log 50.6%

  15. Variation Within a Log

  16. Effects of Initial Planting Spacing • Five replications in a Latin square design. • In each plot, a total of 49 trees were first established as experimental trees • Planted in 1949 • Respaced in 1960 before canopy closure • 3 trees per plot selected • 24 plots used • 72 trees in total

  17. Spacing Examples 18x18 12x18 12x12 6x6

  18. Timber Stiffness

  19. Timber Strength

  20. Benchmarking the Resource • No large-scale systematic study of the variation in wood properties between sites had been undertaken in UK • 64 sites chosen throughout Scotland and northern England • Sites were selected based on: • Elevation • Spacing • Thinning • Yield Class • Latitude • Longitude • Age (35-45 years old)

  21. Measurements • Standing tree acoustic velocity • Stem straightness • Tree size • Stand density • Breast height cores

  22. Variation in Dynamic MOE

  23. Analysis of Cores • Microfibril angle and density from NIR, ITRAX and Silviscan • Wood anatomy determined from image analysis, e.g., • Cell wall thickness • Lumen diameter • Fibre dimensions

  24. Data Analysis • Quantify extent of variation in key wood properties • Identify which factors are important drivers of this variation • Where are the trees with superior wood properties located? • Provide data for testing and refinement of timber properties model • Undertake destructive sampling to validate results from standing tree assessment

  25. Matching Properties to End Uses • Important to match wood properties to most appropriate end use • Low MOE wood sent to non-structural uses • Higher MOE wood sent to structural uses • More home-grown material used in timber frame construction • Higher value end uses - engineered wood products: • SIPS – Structural Insulated Panel Systems • CIB – Composite Insulated Beams • Glulam • I-joists • LVL • Massive wood • Brettstapel

  26. Conclusions • There is a lot to learn about the wood properties of Sitka spruce and the drivers of variation in these properties • Considerable variation in wood properties exist between sites, within sites and within logs • Further processing studies required to verify initial results from benchmarking project • Are the drivers of variation in wood properties additive, or are there strong interactions between them?

  27. Conclusions • Improving wood stiffness is critical for increasing the use of locally-grown timber • It should be possible to do this through prudent forest management and silviculture • Achieving economic yields of C24 is a huge challenge • Knowledge of physical and mechanical properties of home grown timber is essential for using it in engineered wood products

  28. Acknowledgements • Scottish Funding Council • Forest Research • Forestry Commission • The Scottish Forestry Trust • James Jones and Sons Ltd • Balcas Sawmills • Adam Wilson and Sons Ltd • Howies Sawmill

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