Civil Engineering Reference
In-Depth Information
Face knot
(a)
(e)
Edge knot
Shake
(b)
(f)
Wane
(c)
(g)
Surface check
(d)
(h)
End splits
FIGURE 10.8
Common defects in lumber: (a) knots, (b) shakes, (c) wanes,
(d) checks and splits, (e) bowing, (f) crooking, (g) cupping, and (h) twisting.
Reaction Wood
is abnormally woody tissue that forms in crooked
stems or limbs. Reaction wood causes the pith to be off center from
the neutral axis of the tree. It creates internal stresses which can
cause warping and longitudinal cracking.
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