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Eurocode 5: Compression perpendicular to the Grain

Eurocode 5: Compression perpendicular to the Grain. H J Larsen Denmark A J M Leijten TU-Eindhoven – The Netherlands T A C M van der Put TU-Delft – The Netherlands. Acknowledsments. Based on paper for CIB-W18 2008 by H J Larsen, Denmark A J M Leijten, TU-Eindhoven – The Netherlands

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Eurocode 5: Compression perpendicular to the Grain

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  1. Eurocode 5: Compression perpendicular to the Grain H J Larsen Denmark A J M Leijten TU-Eindhoven – The Netherlands T A C M van der Put TU-Delft – The Netherlands

  2. Acknowledsments Based on paper for CIB-W18 2008 by H J Larsen, Denmark A J M Leijten, TU-Eindhoven – The Netherlands T A C M van der Put, TU-Delft – The Netherlands

  3. Problem Introduction of a ”scientific” test method and definition for compression perpendicular to grain has halved the characteristic strength

  4. Problem Introduction of a ”scientific” test method and definition for compression perpendicular to grain has halved the characteristic strength Many traditional structures and details e. g. in timber frame houses will no longer be acceptable

  5. 51x51x152mm 45 51 152 Standard Test Methods ASTM – D143 Australian (technological) test European (scientifical) test EN 408 Compressive strength = Poussa et all. Proc.:CIB-W18-2007: paper 40-2-2

  6. Standard Test Methods Compressive stress

  7. 1 % Definition Compressive strength European test EN 408 1% off-set Compressive strength

  8. Comparison of test results Ref: Poussa et al. Helsinki CIB-W18 paper 40-2-2

  9. ProposalThelandersson & Mårtensson and others Regard exceedance of scientific compression strength as violation of a serviceability state (and not an ultimate limit state)

  10. Limit states Ultimate limit states Serviceability limit states

  11. Ultimate limit states Failure of whole structure or part of it Precise internationally agreed definitions On the whole agreed safety level

  12. Topping-up day

  13. Next day - failure

  14. Failure (at least in lower story)

  15. Failure (at least in lower story)

  16. Deformations preceding failure

  17. Serviceability limit states Unacceptable behaviour at normal use

  18. Serviceability limit states Unacceptable behaviour at normal use, e. g. visually unacceptable

  19. Serviceability limit states Unacceptable behaviour at normal use, e. g. visually unacceptable

  20. Serviceability limit states Unacceptable behaviour at normal use, e. g. visually or functionally unacceptable deformations

  21. Serviceability limit states In most cases: No precise requirements Criteria fixed by designer in agreement with client National tradition and taste

  22. Serviceability limit states Formally it is not required to perform a serviceability verification as long as it is possible to perform the ultimate state verification

  23. Serviceability, compression perp. It is difficult, to put it mildly, to understand why exceeding a marginal deformation in a block compression test should be taken as the governing criteria for structures where much larger deformations are normally acceptable and loaded in a completely different way.

  24. Serviceability, compression perp. It is difficult, to put it mildly, to understand why exceeding a marginal deformation in a block compression test should be taken as the governing criteria for structures where much larger deformations are normally acceptable and loaded in a completely different way. Especially when the use of the Serviceability limit state is accepted only half heartedly and without a proper definition and understanding

  25. Eurocode design equation EN1995-1-1 Impirical model Hilmer Riberholt Incomplete, discontinous, strange jumps

  26. l + 60mm New design equation EN1995-1-1:2005/A1 Blass and Görlacher based on Borg Madsen (2000) lef =

  27. Alternative Model Based on Van der Put (1986) Slip-line theory

  28. Alternative Model Slope 1:1 for 1% off-set Slope 1:1,5 for 10% deformation

  29. Alternative Model Based on Van der Put (1986) Slip-line theory (Schoenmakers)

  30. A B C D E F Model comparison Load cases reported • Test results reported by many authors • Test A: n = 418 • Tests B to F: 1% n= 582 (52 samples) • 10% n= 125 (23 samples) • Solid wood • Glued laminated wood

  31. Comparison 1 % off-set

  32. Model comparison

  33. Comparison

  34. Comparisonsln(model/test)=ln(R) ideally: ln(R)=0  R=1

  35. Model evaluation

  36. Model evaluation

  37. Conclusion Compression perpendicular to grain The evaluation of both models show that Van der Put model is far more accurate in predicting accurately the bearing strength perpendicular to the grain than the model currently in Eurocode 5/A1.

  38. Proposal for EC5 adoption Compression perpendicular to grain for h < 4 b Deformation limit 1% Deformation limit 10%

  39. Proposal for EC5 adoption Compression perpendicular to grain for h < 4 b Deformation limit 1% Deformation limit 10%

  40. Restriction Formally verified only for continously supported beams

  41. Restriction Formally verified only for continously supported beams Not too difficult to extend to concentrated supports

  42. Future Formally verified only for continously supported beams Not too difficult to extend to concentrated supports No tests for unsupported loads

  43. Future Tests needed for unsupported loads !

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