Eurocode 5 compression perpendicular to the grain
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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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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

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


Problem

Problem

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


Problem1

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


Standard test methods

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


Standard test methods1

Standard Test Methods

Compressive stress


Definition compressive strength

1 %

Definition Compressive strength

European test

EN 408

1% off-set

Compressive strength


Comparison of test results

Comparison of test results

Ref: Poussa et al. Helsinki CIB-W18 paper 40-2-2


Proposal thelandersson m rtensson and others

ProposalThelandersson & Mårtensson and others

Regard exceedance of scientific compression strength as violation of a serviceability state (and not an ultimate limit state)


Limit states

Limit states

Ultimate limit states

Serviceability limit states


Ultimate limit states

Ultimate limit states

Failure of whole structure or part of it

Precise internationally agreed definitions

On the whole agreed safety level


Topping up day

Topping-up day


Next day failure

Next day - failure


Failure at least in lower story

Failure (at least in lower story)


Failure at least in lower story1

Failure (at least in lower story)


Deformations preceding failure

Deformations preceding failure


Serviceability limit states

Serviceability limit states

Unacceptable behaviour at normal use


Serviceability limit states1

Serviceability limit states

Unacceptable behaviour at normal use, e. g.

visually unacceptable


Serviceability limit states2

Serviceability limit states

Unacceptable behaviour at normal use, e. g.

visually unacceptable


Serviceability limit states3

Serviceability limit states

Unacceptable behaviour at normal use, e. g.

visually or functionally unacceptable deformations


Serviceability limit states4

Serviceability limit states

In most cases: No precise requirements

Criteria fixed by designer in agreement with client

National tradition and taste


Serviceability limit states5

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


Serviceability compression perp

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.


Serviceability compression perp1

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


Eurocode design equation

Eurocode design equation

EN1995-1-1

Impirical model

Hilmer Riberholt

Incomplete, discontinous, strange jumps


New design equation

l + 60mm

New design equation

EN1995-1-1:2005/A1

Blass and Görlacher based on

Borg Madsen (2000)

lef =


Alternative model

Alternative Model

Based on Van der Put (1986)

Slip-line theory


Alternative model1

Alternative Model

Slope 1:1 for 1% off-set

Slope 1:1,5 for 10% deformation


Alternative model2

Alternative Model

Based on Van der Put (1986)

Slip-line theory

(Schoenmakers)


Model comparison

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


Comparison 1 off set

Comparison 1 % off-set


Model comparison1

Model comparison


Comparison

Comparison


Comparisons ln model test ln r ideally ln r 0 r 1

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


Model evaluation

Model evaluation


Model evaluation1

Model evaluation


Conclusion

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.


Proposal for ec5 adoption

Proposal for EC5 adoption

Compression perpendicular to grain

for h < 4 b

Deformation limit 1%

Deformation limit 10%


Proposal for ec5 adoption1

Proposal for EC5 adoption

Compression perpendicular to grain

for h < 4 b

Deformation limit 1%

Deformation limit 10%


Restriction

Restriction

Formally verified only for continously supported beams


Restriction1

Restriction

Formally verified only for continously supported beams

Not too difficult to extend

to concentrated supports


Future

Future

Formally verified only for continously supported beams

Not too difficult to extend

to concentrated supports

No tests for unsupported

loads


Future1

Future

Tests needed

for unsupported loads

!


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