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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
Load carrying modelfor CLT loaded in bending
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
8,0,,0,/4,,, klthGLTCLTsyskcm fakkkf
16
Load carrying modelfor CLT loaded in bending
Model for CLT
94,00,29
3,27
05,,
05,,/
GLTm
CLTEdgeGLTCLT f
fk
8,0,,0,/4,,, klthGLTCLTsyskcm fakkkf
17
Model for CLT
94,00,29
3,27
05,,
05,,/
GLTm
CLTEdgeGLTCLT f
fk
1,14, sysk
8,0,,0,/4,,, klthGLTCLTsyskcm fakkkf
Load carrying modelfor CLT loaded in bending
18
Load carrying model for CLT in bending - based on test results
8,0,,0,/4,,, klthGLTCLTsyskcm fakkkf
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
Load carrying modelfor CLT loaded in bending
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
Load carrying modelfor CLT loaded in bending
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
Determination of stresses inCLT-elements loaded in bending
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
Determination of stresses inCLT-elements loaded in bending
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
Determination of stresses inCLT-elements loaded in bending
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
Determination of stresses inCLT-elements loaded in bending
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
Determination of stresses inCLT-elements loaded in bending
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
Inffeldgasse 24, A-8010 Graz / Austria