Your SlideShare is downloading. ×
Session 5 ic2011 vestol
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×

Saving this for later?

Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime - even offline.

Text the download link to your phone

Standard text messaging rates apply

Session 5 ic2011 vestol

270
views

Published on

Published in: Business, Technology

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
270
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
4
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. APPLICABILITY OF EUROPEANSTANDARDS FOR STRUCTURAL TIMBER ON SCOTS PINE ROUND TIMBER Geir I. Vestøl & Olav Høibø
  • 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. NORWEGIAN UNIVERSITY OF LIFE SCIENCES Site effects on density and MoE 14 www.umb.no
  • 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. 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. 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. 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. 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. 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. 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