WOOD - Materials for Civil and Construction Engineers - page 437

or whether the wood in the laminate is visually graded or stress graded.
Species may be specified in combination with these stress classes to obtain
the required design properties. The presence of a stress classification does
not ensure that the material is available. In addition, higher design values for
some properties may be obtained by specifying a specific combination of
laminations. Table 10.12 presents a partial list of allowable design stresses
for glulams, with four or more laminations, used as bending members that
are commonly produced by members of the APA-EWS. The species of wood
in this table are
ES: Eastern spruce
DF: Douglas fir
SP: Southern pine

y y

Flange

t t

Web

Web

cd

X X cd X X

y y

t t

b
2

b
2

W b W

Box beam

2W

I beam

(b)

(a)

t 1

Stringers

t c

d

Plywood skins

t 2

b

(c)

Structural panel sheathing

Foam core

(d)

FIGURE 10.21 Composite structural members (a) box beam, (b) I-beam,
(c) stressed skin panel, and (d) structural insulated panel.