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# Eurocode 5: Compression perpendicular to the Grain PowerPoint PPT Presentation

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

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

T A C M van der Put, TU-Delft – The Netherlands

### Problem

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

### 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

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 Methods

Compressive stress

1 %

### Definition Compressive strength

European test

EN 408

1% off-set

Compressive strength

### Comparison of test results

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

### ProposalThelandersson & Mårtensson and others

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

### Limit states

Ultimate limit states

Serviceability limit states

### Ultimate limit states

Failure of whole structure or part of it

Precise internationally agreed definitions

On the whole agreed safety level

### Serviceability limit states

Unacceptable behaviour at normal use

### Serviceability limit states

Unacceptable behaviour at normal use, e. g.

visually unacceptable

### Serviceability limit states

Unacceptable behaviour at normal use, e. g.

visually unacceptable

### Serviceability limit states

Unacceptable behaviour at normal use, e. g.

visually or functionally unacceptable deformations

### Serviceability limit states

In most cases: No precise requirements

Criteria fixed by designer in agreement with client

### 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.

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 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

EN1995-1-1

Impirical model

Hilmer Riberholt

Incomplete, discontinous, strange jumps

l + 60mm

### New design equation

EN1995-1-1:2005/A1

Blass and Görlacher based on

lef =

### Alternative Model

Based on Van der Put (1986)

Slip-line theory

### Alternative Model

Slope 1:1 for 1% off-set

Slope 1:1,5 for 10% deformation

### Alternative Model

Based on Van der Put (1986)

Slip-line theory

(Schoenmakers)

A B C D E F

### Model comparison

• 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

### 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.

Compression perpendicular to grain

for h < 4 b

Deformation limit 1%

Deformation limit 10%

Compression perpendicular to grain

for h < 4 b

Deformation limit 1%

Deformation limit 10%

### Restriction

Formally verified only for continously supported beams

### Restriction

Formally verified only for continously supported beams

Not too difficult to extend

to concentrated supports

### Future

Formally verified only for continously supported beams

Not too difficult to extend

to concentrated supports

No tests for unsupported

Tests needed