APPLICABILITY OF EUROPEANSTANDARDS FOR STRUCTURAL TIMBER   ON SCOTS PINE ROUND TIMBER        Geir I. Vestøl & Olav Høibø
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                            Outline                                  ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                            Possible use of low quality Scots pine   ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                            Strength of round timber                 ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                            Strength grading                         ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                            European standards regarding strength gra...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                                                        EN 14081-1   ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                            European standards applicable on round ti...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                        Visual grading of Scots pine round timber    ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                        Tested materials                             ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                        Uncorrected values of density, MoE and MoR   ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                        EN 338 – Strength classification             ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                        Site effects on density and MoE              ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                        Site effect on bending strength              ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                            Corrections according to EN 384          ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                        MoE and MoR models                           ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                        MoE, Correction for moisture content         ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                        MoR, Correction for moisture content         ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                        MoR, Correction for dimension                ...
NORWEGIAN UNIVERSITY OF LIFE SCIENCES                                        Conclusions                                  ...
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Session 5 ic2011 vestol

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Session 5 ic2011 vestol

  1. 1. APPLICABILITY OF EUROPEANSTANDARDS FOR STRUCTURAL TIMBER ON SCOTS PINE ROUND TIMBER Geir I. Vestøl & Olav Høibø
  2. 2. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Outline   Background –  Use of low quality Scots pine in Norway –  Strength grading of structural timer in Europe   Structural round timber of Scots pine from Norway –  Mechanical properties –  Strength grading –  Applicability of European Standards on round timber 2 www.umb.no
  3. 3. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Possible use of low quality Scots pine   Pulp and paper   Particleboard, fiberboard   Energy   Structural round timber 4 www.umb.no
  4. 4. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Strength of round timber   Stronger than sawn timber because of fiber continuity in the surface   Juvenile core is surrounded by mature wood that is denser, stiffer and stronger. 5 www.umb.no
  5. 5. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Strength grading   Strength grading is allocation of timber pieces into strength classes with defined properties   European standardization –  Requirements for density, stiffness properties and strength properties –  Measurements and calculations –  Visual grading –  Machine grading 6 www.umb.no
  6. 6. NORWEGIAN UNIVERSITY OF LIFE SCIENCES European standards regarding strength grading   EN 14081: Strength graded structural timber with rectangular cross section, part 1-4   EN 338: Strength classes   EN 408: Determination of some physical and mechanical properties   EN 384: Determination of characteristic values of mechanical properties and density   National/regional visual grading rules –  INSTA 142: Nordic visual strength grading rules for sawn timber 7   EN 1912: Assignment of visual grades and species www.umb.no
  7. 7. NORWEGIAN UNIVERSITY OF LIFE SCIENCES EN 14081-1 Strength graded structural timber with rectangular cross section. Part 1: General requirements   INSTA 142 EN 14081-4 Nordic visual strength grading Strength graded structural rules for sawn timber timber with rectangular cross section.  EN 1912 Part 4: Machine grading – grade Assignment of visual grades machine settings for machine and species controlled settings   EN 338 Strength classes 8  Eurocode 5 www.umb.no
  8. 8. NORWEGIAN UNIVERSITY OF LIFE SCIENCES European standards applicable on round timber?   EN 338: Strength classes   EN 14251: Structural round timber - Test methods –  (Corresponds to EN 408)   EN 384: Determination of characteristic values of mechanical properties and density –  Corrections for moisture content, dimensions and sample size   National/regional visual grading rules   Missing: –  EN 1912: Assignment of visual grades and species 9 –  Machine grading www.umb.no
  9. 9. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Visual grading of Scots pine round timber   Ranta-Maunus (1999) –  A: C30 (Scots pine and Norway spruce) –  B: C18 (Scots pine) –  Strength reducing characteristics, geometrical characteristics, biological characteristics   Boren & Barnard (2000) –  C30 (Scots pine) –  C24 (Scots pine) –  Knot size, knot sum, annual ring width, tapering 10 www.umb.no
  10. 10. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Tested materials   Density, modulus of elasticity and bending strength   Visual characteristics   533 logs –  75 mm – 250 mm –  Sampled from 150 trees from 10 locations –  All logs with diameter >75 mm tested 11 www.umb.no
  11. 11. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Uncorrected values of density, MoE and MoR   Some correlation between dimension and moisture content (r = 0.552)   Strong, even if poor quality www.umb.no 12
  12. 12. NORWEGIAN UNIVERSITY OF LIFE SCIENCES EN 338 – Strength classification (Vestøl & Høibø, 2010)   Strength class is limited by MoE   Should be possible to obtain C40 by rejecting only a small number of pieces www.umb.no 13
  13. 13. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Site effects on density and MoE 14 www.umb.no
  14. 14. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Site effect on bending strength   It is not possible to obtain C40 from all sites without rejecting a large number   Models showed that visual grading left significant effects of site   Predicting MoR from MoE is more accurate, and not as dependent on site 15 (Vestøl & Høibø, 2010) www.umb.no
  15. 15. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Corrections according to EN 384   MoE is corrected for moisture content –  Correction coefficient = 0.02   MoR is not corrected for moisture content   MoR is corrected for dimension by dividing on " 150 % 0.2 kh = $ # D& 16 ! www.umb.no
  16. 16. NORWEGIAN UNIVERSITY OF LIFE SCIENCES MoE and MoR models   Y= +f(A,B,C…)+Si+ ij –  f(A,B,C…) = covariate function –  Si = random effect of site (i = 1–10)   Tested covariates –  Density, annual ring width, grain angle –  Maximum knot size, relative maximum knot size –  Maximum knot group, relative maximum knot sum –  Tapering –  Moisture content –  Dimension 17 www.umb.no
  17. 17. NORWEGIAN UNIVERSITY OF LIFE SCIENCES MoE, Correction for moisture content   MoE = f(MC, density, tapering, knot sum) –  Fixed effects model: •  RMSE = 1953 N/mm2, R2 = 0.61 –  16.0% of random variance due to site   The model predicts a correction for moisture content –  Average correction coefficient: 0.02 (as in EN 384) 18 www.umb.no
  18. 18. NORWEGIAN UNIVERSITY OF LIFE SCIENCES MoR, Correction for moisture content   MoR = f(MC, ln(D), ln(density), tapering, knot size, knot sum, grain angle) –  Fixed effects model •  RMSE = 6.1 N/mm2 , R2 = 0.75 –  11.3% of random variance due to site   The model predicts corrections for both moisture content and dimension –  Average correction coeffisient for moisture content: 0.04 19 www.umb.no
  19. 19. NORWEGIAN UNIVERSITY OF LIFE SCIENCES MoR, Correction for dimension   MoR = f(MC, ln(D), ln(density), tapering, knot size, knot sum, grain angle) –  Fixed effects model •  RMSE = 6.1 N/mm2 , R2 = 0.75 –  11.3% of random variance due to site   The model predicts corrections for dimension as described in EN 384 " 150 % 0.192 kh = $ # D& ! 20 www.umb.no
  20. 20. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Conclusions   Visual grading leaves significant residuals due to site that cannot be accounted for. –  Visual grading rules have to be either conservative or limited to timber from a specific region.   The model indicates that MoE of round timber can be corrected for moisture content as described in EN 384.   The model indicates that bending strength can be corrected for dimension as described in EN 384, but it should also be corrected for moisture content.   The correction coefficients should be estimated from a controlled experiment without correlation between dimension and moisture content 21 www.umb.no
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