Hardwood Wood Structure Softwood 1 Variability in wood

Hardwood Wood Structure Softwood 1

Variability in wood products frequency Solid wood strength 2

Variability in wood products mean frequency lower 5 th percentile Solid wood ÷ safety factors allowable design stress strength 3

Variability in wood products mean frequency lower 5 th percentile ÷ safety factors Solid wood lower 5 th percentile Wood composite A ÷ safety factors allowable design stress strength 4

Anisotropy (St. Regis Paper Co. ) (Indospectrum. com) (Côté) 5

Anisotropy Parallel to grain Perpendicular to grain

Wood sections/surfaces/planes Transverse section T R R T L Longitudinal section L T T L T = tangential R = radial L = longitudinal

Anisotropy – perpendicular to grain Radial Tangential

Hygroscopicity H Hydrogen Bond O H Water H O H

Wood Hygroscopicity H Hydrogen Bond O H O H

Water in cell wall H H O O O HH H O H H H O O H O H O H H H O H O O H H

Water in wood Cell wall Oven dry 0% m. c. Cell lumen Bound water 0 – 30% m. c. Free water > Fibre saturation point > 30% m. c.

Effect of moisture content on wood properties Fibre Saturation Point

Comparative Environmental Impact Assessment Life Cycle Analysis Canadian Wood Council 14

Comparative Environmental Impact Assessment Canadian Wood Council 15