Civil Engineering Reference
In-Depth Information
Table 20.3
(
Continued
) Sheathing Wet or Damp Location Assumed
Class I formwork, single use or light construction
Class II formwork, multiple use or heavy construction
Allowable unit stress, psi
Allowable unit stress, psi
Species and
Modulus
Modulus
grade of
Extreme
of
Extreme
of
form framing
fiber
Compression
Compression
Horizontal
elasticity,
fiber
Compression
Compression
Horizontal
elasticity,
lumber
bending
⊥ to grain
´
to grain
shear
psi
bending
⊥ to grain
´
to grain
shear
psi
Plywood
Douglas fir,
(Bearing
(Bearing
concrete
on face)
on face)
form B-B
2000
435
1500
*
1,600,000
1500
325
1100
*
1,600,000
10
11
10
11
Board
Use
Use 67% of
Use 90% of
Use
Use
of
Use
Use 67% of
Use 90% of
Use
Use
of
sheathing,
100% of
value for
value for
100% of
value
100% of
value for
value for
100% of
value for
all species
value for
species,
species,
value for
for
value for
species,
species,
value for
species,
species,
shown
shown
species,
species,
species,
shown
shown
species,
shown
shown
above
above
shown
shown
shown
above
above
shown
above
above
above
above
above
above
Sources:
Derived from “National Design Specifications for Stress-Grade Lumber and Its Fastenings,” 1960 edition, as amended, and from “Recommendations of the Douglas Fir
Plywood Association.”
*Shear is not a governing design consideration for plywood form panels except in the case of very short, heavily loaded spans. If 1-in. or
1
8
-in.
panels are being used, check for
rolling shear according to plywood manufacturer's suggestions.
