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Wood Structure. Softwood. Hardwood. Variability in wood products. Solid wood. frequency. strength. Variability in wood products. mean. lower 5 th percentile. Solid wood. ÷ safety factors. frequency. allowable design stress. strength. Variability in wood products. mean. mean. - PowerPoint PPT Presentation
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Wood StructureHardwood Softwood
Variability in wood products
freq
uenc
y
strength
Solid wood
2
Variability in wood products
strength
Solid woodlower 5th percentile
mean
3
÷ safety factors
allowable design stress
freq
uenc
y
Variability in wood productsfr
eque
ncy
strength
Solid woodlower 5th percentile
mean
÷ safety factors
allowable design stress
allowable design stress
lower 5th percentile
÷ safety factors
Wood composite A
mean
4
5
Anisotropy
(Indospectrum.com)(St. Regis Paper Co.)
(Côté)
Anisotropy
Parallel to grain Perpendicular to grain
T
R
TR
TR
T
R
LLL
T = tangentialR = radialL = longitudinal
Wood sections/surfaces/planes
Longitudinal section
Transverse section
Anisotropy – perpendicular to grain
Radial
Tangential
Hygroscopicity
H
O
H
H
O
H
HydrogenBond
Water
Hygroscopicity
O
H
H
H
Woo
dHydrogenBond
O
OH
OH
OH O
H
OH
OH
Water in cell wall
OH
OH
OH O
H
OH
OH
OH
HO
H
H
OH
H
OH
H
OH
H
OH
H
Water in wood
Bound water Free waterCell wall Cell lumen
Oven dry > Fibre saturation point0% m.c. 0 – 30% m.c. > 30% m.c.
Effect of moisture content on wood propertiesFibre Saturation Point
Comparative Environmental Impact AssessmentLife Cycle Analysis
14Canadian Wood Council
Comparative Environmental Impact Assessment
15Canadian Wood Council
