m. augustin institute for timber engineering and wood technology graz university of technology cross...

M. AUGUSTINInstitute for Timber Engineering and Wood TechnologyGraz University of Technology

CROSS LAMINATED TIMBER (CLT)AND THE AUSTRIAN PRACTICE

Educational Materials for Designing andTesting of Timber Structures – TEMTIS

SeminarHorsens / Denmark, 11th September 2008

3

Cross Laminated Timber – Basic idea and Product

Cross Laminated Timber (CLT) - ElementC om posite of longitudinal and transversalsingle layers

Length o f the e lem ent (due to production restrictions) up to 16.5 m

w ith genera l finger-jo in ts due to transportation restrictions up to 30 m possib le

W idth of the e lem ent (due to production restrictions) approx. 3 m

due to transport and assem bling restrictions up to 4 .8 m possib le

Thickness of the e lem ent: 42 m m - 500 m m

G luing of the w hole singlelayer w ith an approvedadhesive

Longitudina l layers usually C 24 or C 30

Transversal layers usually C 16 (up to C 30)>

Tensile strength, tensileM O E and density areincreasing in genera lfrom the p ith to the outerside of the log

Utilisation ofboards from theouter side of thelog (’s ide boards’)

Distribution of mechanical propertiesin the log

5-layered CLT-element

Utilisation of side-boards

4

CLT –Production volume

Production volume:

2008 About 400.000 m³ (+52 %)

→ To high amount for the market

→ Price will decrease (about 20 % in the next three years)

Source: Timber Online / 2007

Arguments PRO CLT:

→ Massive construction, less layers in theconstruction, buffer for heat and moisture

→ High degree of prefabrication possible

→ Easy assembling and short duration for erection

→ Flexibility of utilisation

Arguments CONTRA CLT:

→ High price

5

CLT –Examples of erected buildings

“Austria-House” (2006)

Turin / Italy

Building Research Centre Step 2 (2007)Graz / Austria

6

CLT –Examples of erected buildings

Multi-storey building (2001)

Vienna / Austria

“Wandritsch-Bridge” (1998)

St. Lorenzen / Austria

7

AREA 1_SSTC

Shell and Spatial Timber Constructions (SSTC) TMC using CLT

MODULE 2 Connection Technique

MODULE 4 Development of SystemsArchitectural PotentialCase Studies

MODULE 3 GuidelinesBuilding PhysicsLeading Details

MODULE 1 Mechanical AspectsStructural AnalysisVerification Procedure

R&D-Activities concern. CLT – Institutefor Timber Engineering and Wood Technology /

holz.bau forschungs gmbH // TUG

8

R&D-Activities concern. CLT – Institutefor Timber Engineering and Wood Technology /

holz.bau forschungs gmbH // TUG

Limit states

Topics: “System effects“ “Laminating effects“

Subproject

“Load carrying capacity“(for elements loaded as plates and panels)

Topic: Creep behaviour

Subproject

“Creep“

ObjectiveLoad carrying model CLT Deformation factor CLT

Ultimate Limit State Serviceability Limit State

Further tests:

Properties perpendicular to grain Vibration properties of CLT-floors

9

CLTin standards

Eurocode 1995-1-1

Currently no proposals for the verification of CLT-elements

DIN 1052-2004.08

A verification procedere is given in this standard

1,,

dm

m

dt

t

ff

Verification of stresses on each single layer:

kmkt ff ,,0, 6,0 in accord. with EN 338D

→ This procedere leads to conservative results because no “homogenisation effects“ are considered !

→ The development of an European standard is initiated by the Austrian Standardisation Organisation (ON).

10

Applied to layered products: e.g. Glulam

132

35

35

35

53

,,,,,

dm

m

dm

mm

dm

mt

dm

m

dm

t

fht

fht

hth

fff

h

tmm

h

thmt

-35%

165,0

1523

32

35

,,,

dm

m

dm

m

dm

m

fffht

11

Subproject“Load carrying capacity of CLT in bending“

Objective of the research work

Results of tension tests:

ft,0,l,05 = 12,5 N/mm²

COVt = 39,4 %

Method

12

Testresults

0,00

5,00

10,00

15,00

20,00

25,00

30,00

35,00

40,00

45,00

1 2 3 4 5 6 7 8

Number of lamellas in the outer layers

Mean value and COV of edge normal strength fm,c

f m,c

,me

an [

N/m

m²]

5 # series ‚4u‘ fm,g,mean = 42,4 N/mm² COV = 9,5 %

19 # series ‚1u‘ fm,g,mean = 44,2 N/mm² COV = 20,1 %

37,2

39,0 39,4

37,3

mean value

0,0%

2,0%

4,0%

6,0%

8,0%

10,0%

12,0%

14,0%

16,0%

18,0%

CO

V [

%]

16,1%

14,4% 12,5%

7,6%

COV

13

5 % - quantile valuesand system factor for CLT

Number of lamellas in the outer layers

f m,c

,05 [

N/m

m²]

25,00

26,00

27,00

28,00

29,00

30,00

31,00

32,00

33,00

34,00

1 2 3 4 5 6 7

5% fractile and ksys of edge normal strength fm,c

8

k sy

s,C

LT

1,00

1,05

1,10

1,15

1,20

1,25

1,30

1,00

1,09

1,141,19

system effect

27,3

29,8

31,3

32,6

5% fractile

19 # series ‚1u‘ fm,g,05 = 29,0 N/mm²

1,1

proposal ksys

14

Beam Model for GLT

kltkgm ff ,,0,,, 15,10,7

35,0811,2

25,0422,2

t

tGLT COV

COVa

including the variation of the base material

82,0,,0,,, kltGLTkgm faf

8,0,,0,,, 0,44,106,1 klttkgm fCOVf

a

8,0,,0,/4,,, klthGLTCLTsyskcm fakkkf

according to EN 1194:1999

e.g.:

Load carrying modelfor CLT loaded in bending

15


Beam Model for GLT

kltkgm ff ,,0,,, 15,10,7

35,0811,2

25,0422,21

t

t

COV

COVa

including the variation of the base material

82,0,,0,1,, kltkgm faf

18,1110

6006001,01,0

h

kh

8,0,,0,,, 0,44,106,1 klttkgm fCOVf


16


Model for CLT

94,00,29

3,27

05,,

05,,/

GLTm

CLTEdgeGLTCLT f

fk


17

Model for CLT

94,00,29

3,27

05,,

05,,/

GLTm

CLTEdgeGLTCLT f

fk

1,14, sysk



18

Load carrying model for CLT in bending - based on test results


20,1110

150

110

60015060005,01,005,01,0

bhkh

15,3394,00,44,106,10,44,106,1 tCOVa

Test results 31,3

29,6

1,1

ksys

Analy. results

Factor

12,5

12,5

ft,0,l,05

-

23,8

3,15

a (COVt = 39,4 %)

29,0

28,6

1,20

kh (h = 110 mm,

b = 110 mm)

27,3

26,9

0,94

kCLT/GLT


20

Proposal of a Beam Model for CLT – Comparison with older data

8,0,,0,4,,, 0,576,1 klttkcm fCOVf

Single result of one 9 layer CLT element (width 2000 mm); 3)

Single result of one 7 layer CLT element (width 2000 mm); 2)

37,5

39,1 2)

42,9 2)

39,4 3)

~ 35 %19,3

(n = 80)

old results (1998)

26,8 (n = 50) 45,547,830,4 %New results 1)

5 layer CLT made of solid edge glued panels (spruce); 1)

[N/mm²][N/mm²][%][N/mm²]

12,5

ft,0,l,05

28,131,339,4 %presented

fm,c,05,≥4

calculated

fm,c,05,=4

test resultsCOVt


21

Verification intechnical approvals

Specifications intechnical approvals

1,

, dml

dm

fk

22

Comparison ofverification approvals

1,

,

,

,

dm

dm

dt

dt

ff

165,065,0

,mod

,

,

,

kmM

dm

dm

dm

fkf

1

8,0,,0,

mod

,

,,

,

kltCLT

M

dm

dcm

dm

fakf

DIN

105

2

C 24ft,0,l,k = 14,0

COV = 35 %

C 40ft,0,l,k = 24,0

COV = 25 %

15,6

0,65∙fm,k

26,0

0,65∙fm,k

29,0

1,21∙fm,k

38,3

0,96∙fm,k

Comparison of verification proposals

Pro

posa

l TU

G

23

Determination of stresses inCLT-elements loaded in bending

Shear stresses

eff

eff

V Sz

I b

Seff

Normal stresses

E

Ez

I

Mz i

eff

Ieff

Determination of stresses for CLT

24

,

1 1ges

eff Geff

w MMds VVdsAE I

G

,

1 1ges

eff Geff

w MMds VVdsAE I

G

kAG,effSeffIeff

Ratio of shear-deformation on the total deflection

(single-span beam with uniformly distributed load)

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

10 15 20 25 30 35

Ratio l / h

Rat

io w

V /

wg

es

be

am

Are

a o

f u

tili

sa

tio

n i

n p

rac

tic

e -

Are

a o

f u

tili

sa

tio

n i

n p

rac

tic

e -

pla

te

isotrop

spruce

CLT 5-layered

Determination of deformationsfor CLT

Determination of deformations ofCLT-elements loaded in bending

25

7

5

3

Number of layers

2i ieff i i i

E EI I A e

E E

390

0

126 1

12 27

Eb h

E

390

0

199 26

12 125

Eb h

E

390

0

1244 99

12 343

Eb h

E

90 0E

3 26

12 27

b h

3 99

12 125

b h

3 244

12 343

b h

90 0E

kAG,effSeffIeff

Effective second moment of area of the cross section


26kAG,effSeffIeff

7

5

3

Number of layers

,i

eff i s iE

S A eE

90 0E

2 8

8 9

b h

2 17

8 25

b h

2 32

8 49

b h

290

0

18 1

8 9

Eb h

E

290

0

117 8

8 25

Eb h

E

290

0

132 17

8 49

Eb h

E

90 0E

Effective statical moment of the cross section


27kAG,effSeffIeff

7

5

3

Number of layers

9090

090

12 1

3

Gb h

G

9090

090

13 2

5

Gb h

G

9090

090

14 3

7

Gb h

G

,i

eff G iG

A AG

090

9090

10G

G

2,1

3b h

3,2

5b h

4,3

7b h

Effective area of the cross section


28

,

1 1ges

eff Geff

w MMds VVdsAE I

G

kAG,effSeffIeff

Shear correction factor κ for CLT cross sections with consideration of the material values in accord. to DIN 1052

1,20

0

1,2

2,4

3,6

4,8

6

1 3 5 7 9 11 13

Number of layers n

Sh

ear

corr

ecti

on

fac

tor

κ

4,874,11 3,88 3,78 3,73 3,70

Shear correction factor


32kAG,effSeffIeff

Material properties

EN 338 (all strength-classes) 1)

C 24 (in accord. with the approvals) 2)

C 30(in accord. with the approvals) 2)

G9090 = G090/10 G9090 = 50 [N/mm2] G9090 = 50 [N/mm2]

3-layered 4,9 6,5 7,0

5-layered 4,1 5,4 5,9

7-layered 3,9 5,1 5,5

1) E0/E90 = 30; E0/G090 = 16; G090/G9090 = 10

2) Für C24: E0/E90 = 30; E0/G090 = 16

Für C30: E0/E90 = 30; E0/G090 = 16

Shear correction factor with values from standards


33

- without openings

CLT wall elements under homogeneous shear (shear stiffness)experimental and theoretical solution (doctoral thesis in process: Th. Moosbrugger)

- with openings

u = 5 mma = 75 mm u/a= 0.067

u a

60 mm

Gplate,mean= 229 N/mm²

(5 tests, COV = 0.16)

board spacing:board width:

u/a=0.067

0.8

≈ 0.29

pra

ctic

al r

ang

e

229 / 750 0.3

Determination of stresses inCLT-elements loaded as panel

34

Creep behaviour ofCLT-elements

Specimens with two cross sections:GLT and CLT

Test setup: 4 – point – bending test according to EN 408

Futher details tests:

Tests with two climates (55%/20°C; 78%/20°C) and two stress levels (about 3 N/mm² and 8 N/mm²)

Sl.1 - low

Sl.2 - highClimate 2

Sl.1 - low

Sl.2 - highClimate 1

GLT CLT

Stress - level

Climate

+ 38,5 %

+ 46,5 %

+ 19,3 %

+41,9 %

Results

kdef,CLT,5-layer

SC 1 0,85

SC 2 1,10

Proposals for standardisation

Approximatly values for Plywood

35

Compression perpendicular to grainof CLT-cubic specimens

Dru

ck-E

last

izitä

tsm

odul

que

r zu

r F

aser

[N/m

m²]

100

10 6722 29 40 50 90

200

300

400

500

600

700

800

D icke der brettförm igen bzw. der E inzellagen der würfe lförm igen P robekörper [m m ]

C

C

EE

A

A

B

B

D

D

E aus [10]c,90,k

E aus [10]c,90,m ean“B ox-P lo ts” der w ürfe l-förm igen P robekörper

“B ox-P lo ts” der bre tt-förm igen P robekörper

Verlau f der M itte lw erte

Verlau f der 5 % -Q uantilw erte

C harakteristische W erte

B ere ich der prax isre levantenS chich td icken

Dru

ckfe

stig

keit

quer

zur

Fas

er[N

/mm

²]

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

10 6722 29 40 50 90

Dicke der brettförm igen bzw. der E inzellagen der würfe lförm igen P robekörper [m m ]

“B ox-P lo ts” der w ürfe l-förm igen P robekörper

“B ox-P lo ts” der bre tt-förm igen P robekörper

Verlau f der M itte lw erte

Verlau f der 5 % -Q uantilw erte

C harakteris tische W erte

f aus [10]c,90,k

f aus [10]c,90,m ean

B ere ich der p rax isre levantenS chichtd icken

Ec,90,mean = 500 N/mm²

fc,90,k = 3,0 N/mm²Strength

Stiffness

Test setup:

Tests on specimens with different number of layers, position of the board in the log, built-up factor and loading situations

THANKS FOR YOUR ATTENTION !

Contact

DI

Manfred AUGUSTINScientific Assistent

+43 (0) 316 873-4604

[email protected]

Inffeldgasse 24, A-8010 Graz / Austria

m. augustin institute for timber engineering and wood technology graz university of technology cross...

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