1 Wood
Wood is the oldest of the structural materials. It has been used since prehistoric times. Wood
can be shaped with simple tools, and it can be easily fastened with nails, screws, or adhesives. It is
available either as lumber, which is a natural wood, or as glued laminated timber. This latter form
is much stronger and consists of specially selected and prepared wood laminations securely
bonded together with glue or adhesives. The laminations do not exceed in thickness. Glued
laminated beams are available in a variety of shapes. Both lumber and glued timber is widely in
building construction.
Wood contains certain natural defects, such as knots, shakes, etc., which require that it be
stress-traded to establish design or allowable stress values for particular members. Another
important factor is the grain of the wood .The allowable stress in compression parallel to the grain,
for instance, is higher than the allowable stress perpendicular to the grain.