1. 6/24/2011
Torsional stiffness of small‐ and
medium‐size samples of cross
laminated timber (CLT) panels:
laminated timber (CLT) panels:
optical measurements and FEM
simulations
Lech Muszyński1
Mélanie Noyel2
Thomas Pisaneschi2 Université H. Poincaré
(University of Nancy)
Václav Sebera3
Benjamin Sundberg1
Rakesh Gupta1
Cross laminated timber (CLT or Xlam)
Kreuzlagenholz (KLH)
http://www.storaenso.com/ d/0607/0607240451/1.php
www.news.janjan.jp/world
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Cross laminated timber
(CLT, KLH or Xlam)
CLT is manufactured in 3, 5, 7 and multilayer
composites with different lumber thicknesses.
h d ff l b h k
Maximum overall thickness: 40 cm.
v=pI3tMQ20mzs&NR=1
Surface can be finished with wood‐based panels
(e.g. sheetrock or plywood) by adhesive bonding
http://www.youtube.com/watch?v
http://www.storaenso.com/
Width: up to 2,95 m
Length: up to 16 m
Thickness: up to 40 cm
Pre‐cutting: cuts for windows, doors, and so on
Wood species: Spruce , Pine or Larch (in EU)
Adhesives: MUF, PRF, PUR
http://www.clt.info/
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4. 6/24/2011
CLT Movies!
http://www.clt.info/
Fast movie
Objectives
To investigate the viability of Oregon Hybrid
Poplar for Cross laminated timber:
Poplar for Cross laminated timber:
– Investigate optimal bonding conditions
– Master manufacturing small and medium scale CLT
samples
– Determine benchmark mechanical characteristics of
Determine benchmark mechanical characteristics of
the samples
– Develop procedures for scaling up results from small‐
scale samples to full‐scale elements
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Materials
• Wood :
Hybrid poplar, Greenwood Tree Farm
Nominal section = 6 x 1 ½ in, 8 ft long
Measured mean characteristics
Moisture content = below 6%
Measured thickness = 34.8 ± 1.4 mm
Density = 295 kg/m‐3 (19.4 cpf)
Elastic modulus = 7.58 GPa (1 1*106 psi)
Elastic modulus 7.58 GPa (1.1 10
• Adhesive :
PRF resin, Hexion Specialty Chemicals, Springfield, OR
Resin : Cascophen LT‐5210J
Hardener : Cascoset FM‐6210
not exactly a structural‐grade timber
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Test procedures
Block shear tests Shear‐bending test based on
Methods: ASTM 3044
modified ASTM D143 (14)
modified ASTM D1037 (81‐86 & 87‐90)
P (dead weight)
Δctr
Sample A Sample B
Δsup
Sample E Sample L
Shear block tests
Variables Specimen geometry
2 adhesive spread rates
2 adhesive spread rates
0.25 kg/m2 (55 lb/1000 ft2)
0.45 kg/m2 (100 lb/1000 ft2)
3 clamping pressures (12 hours) Sample A Sample B
0.34 MPa (50 psi)
0.69 MPa (100 psi)
1.03 MPa (150 psi)
Sample E Sample L
3‐8 specimens per condition, all specimens bonded at MC ~12 %
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7. 6/24/2011
Shear block tests
Specimens:
Shear blocks cut from small 3‐layer CLT billets
bonded w/o surface prep
Shear block test results
Shear along the grains:
5.63 MPa 1.28 MPa
5 63 MP ± 1 28 MP
Sample A
(817 psi ± 186 psi)
“Rolling shear”:
2.80 MPa ± 0.45 MPa
Sample B
(406 psi ± 65 psi)
(406 i ± 65 i)
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Shear block test results
Sample L Sample E Sample B
3.5 3.5
Type L avg Spread rate 0.25 kg/m2 Type E avg Spread rate 0.25 kg/m2
Spread rate 0.45 kg/m2 Spread rate 0.45 kg/m2
3.0 3.0
Rolling shear in clear wood samples 2.80 MPa ±0.45 MPa Rolling shear in clear wood samples 2.80 MPa ±0.45 MPa
ear stress, MPa
ear stress, MPa
2.5 2.5
2.0 2.0
1.5 1.5
Max she
Max she
1.0 1.0
0.5 0.5
0.0 0.0
0.34 MPa (50 psi) 0.69 MPa (100 psi) 1.03 MPa (150 psi) 0.34 MPa (50 psi) 0.69 MPa (100 psi) 1.03 MPa (150 psi)
clamping pressure clamping pressure
No substantial effect of adhesive spread rates
(between 0.25 and 0.45 kg/m2)
Shear block test results
3.5
Type L avg Type E avg
3.0
Rolling shear in clear wood samples 2.80 MPa ±0.45 MPa
Pa
Max shear stress, MP
2.5
2.0 Sample L
1.5
1.0
0.5
Sample E
S l E
0.0
0.34 MPa (50 psi) 0.69 MPa (100 psi) 1.03 MPa (150 psi)
clamping pressure
Weak effect of billet bonding pressure in specimens Type L
Specimen Type L reveals the weakest aspect of the bond
Sample B
(should be preferred in testing)
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Shear block test results
140%
Spread rate 0.45 kg/m2 Type L Type E
ailure
120%
Percent of rolling shear fa
100%
80%
60%
40%
20%
0%
0.34 MPa (a psi) 0.69 MPa (50 psi) 1.03 MPa (100 psi)
clamping pressure
In most cases failure is governed by rolling
shear (regardless of the specimen type)
Test panels manufactured at
3‐layer, 1.22 m x 1.22 m
(4 ft x 8 ft*)
(4 ft x 8 ft*)
*later divided into two 4 ft x 4 ft
Clamping pressure: not measured
PRF Spread rate: 0.45 kg/m2
3 layer, 0.61 m x 0.61 m
3‐layer, 0.61 m x 0.61 m
(2 ft x 2 ft)
glue line ‐
Clamping pressure: 0.83 MPa
PRF Spread rate: 0.45 kg/m2
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10. 6/24/2011
Tests on 4 ft x 4 ft samples
Panel twisting test Deflection measured w/ dial gages
based on ASTM 3044
b d ASTM 3044 Load‐Deflection
12
Repeatibility test
10 Series w/ DIC
Linear (Repeatibility test)
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P = 2.8482Δ
Load, kN
R² = 0.9984
6
4
2
0
0.0 1.0 2.0 3.0 4.0
Δ ctr, mm
Tests on 4 ft x 4 ft samples
Panel twisting test
based on ASTM 3044
b d ASTM 3044
deflection
measured
optically
(DIC)
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Surface topography
Surface topography under load
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Deflection
Deflection paths to be analyzed
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Deflections along ctr vertical
2
0
‐2
Deflection, mm
‐4
‐6
Vertical in Image #20 (P=6 kN)
‐8
Vertical in Image #27 (P=0 kN)
‐10
0 200 400 600 800 1000 1200
Distance along vertical: Y, mm
Deflections along ctr horizontal Deflections along the diagonal
2 2.00
0 0.00
‐2 ‐2.00
Deflection, mm
Deflection, mm
‐4 ‐4.00
‐6 ‐6.00
Horizontal in Image #20 (P=6 kN) Diagonal in Image #20 (P=6 kN)
‐8 ‐8.00
Horizontal in Image #27 (P=0 kN) Diagonal in Image #27 (P=0 kN)
‐10 ‐10.00
0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200
Distance along horizontal: X, mm Distance along diagonal: L, mm
Load‐Deflection
12
Repeatibility test
Measurements
& Simulations
10 Series w/ DIC
Linear (Repeatibility test)
8
P = 2.8482Δ
Load, kN
R² = 0.9984
6
4
2
0
0.0 1.0 2.0 3.0 4.0
Δ ctr, mm
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Simulation:
4 ft x 4 ft panel
Simulations based on measured longitudinal
modulus of the hybrid poplar boards:
7.58 GPa (1.1*106 psi)
Other elastic properties derived from
relations published in 2010 FPL Wood
Handbook for eastern cottonwood and
yellow poplar.
27/28
Deflections along ctr horizontal
2
0
‐2
Deflection, mm
‐4
‐6 DIC (P=6 kN, hybrid poplar)
( y p p )
FEM (P=6 kN, cottonwood)
‐8
FEM (P=6 kN, yellow poplar)
‐10
0 200 400 600 800 1000 1200
Distance along horizontal: X, mm
Deflections along ctr vertical Deflections along the diagonal
0 2
‐1
0
‐2
‐3
‐2
Deflection, mm
Deflection, mm
‐4
‐5 ‐4
‐6
‐6
‐7 DIC (P=6 kN, hybrid poplar)
DIC (P=6 kN, hybrid poplar)
‐8 FEM (P=6 kN, cottonwood)
‐8 FEM (P=6 kN, cottonwood)
FEM (P=6 kN, yellow poplar)
‐9 FEM (P=6 kN, yellow poplar)
‐10 ‐10
0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200
Distance along vertical: Y, mm Distance along diagonal: L, mm
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15. 6/24/2011
Summary
• Bond performance:
– No substantial effect of adhesive spread rates (between
0 25 d 0 45 k / 2)
0.25 and 0.45 kg/m )
– Weak effect of billet bonding pressure in specimens Type L
– Specimen Type L reveals the weakest aspect of the bond
(should be preferred in testing)
– In most cases failure is governed by rolling shear
(regardless of the specimen type)
• G d
Good agreement between FEM simulation and full
tb t FEM i l ti d f ll
field deflection measurements on loaded panels
• Data analysis is pending
Acknowledgements
Mélanie Noyel & Thomas Pisaneschi
graduate interns from ENSTIB (School of Wood Science and Timber Engineering)
graduate interns from ENSTIB (School of Wood Science and Timber Engineering)
division of the Université Henri Poincaré (University of Nancy) in Epinal, France
Milo Clauson, OSU
Lee Jimerson, Collins/GreenWood
Todd Miller, Hexion Specialty Chemicals
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16. 6/24/2011
Questions?
Dark side Bright side
Bucket for
bad ideas
(just half full)
unrealitymag.com swg.stratics.com
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