Civil Engineering Reference
In-Depth Information
Table 20.1
Properties of American Standard Board, Plank, Dimension, and Timber Sizes Commonly Used
for Form Construction (Courtesy of the American Concrete Institute)
American
Standard size
Moment of
Section
Board
inertia (in.
4
)
modulus (in.
3
)
Area of section,
Nominal
in inches
feet per
bh
3
12
bh
2
6
A
bh
(sq. in.)
I
S
size in
b
h
S4S*
linear
inches
19% maximum
foot of
b
h
moisture
Rough
S4S
Rough
S4S
Rough
S4S
piece
3
2
3
4
1
3
4
1
3.17
2.62
0.20
0.12
0.46
0.33
5
2
3
4
1
2
6
1
4.92
4.12
0.31
0.19
0.72
0.52
7
4
3
4
2
3
8
1
6.45
5.44
0.41
0.25
0.94
0.68
9
4
3
4
5
6
10
1
8.20
6.94
0.52
0.32
1.20
0.87
11
4
3
4
12
1
9.95
8.44
0.63
0.39
1.45
1.05
1
1
4
3
2
5
12
4
1
4.08
3.50
0.43
0.29
0.76
0.58
1
4
5
2
5
8
6
1
6.33
5.50
0.68
0.46
1.19
0.92
1
4
7
4
5
6
8
1
8.30
7.25
0.87
0.60
1.56
1.21
1
4
9
4
1
24
10
1
10.55
9.25
1.11
0.77
1.98
1.54
1
4
11
4
1
4
12
1
12.80
11.25
1.35
0.94
2.40
1.87
1
2
3
2
1
4
1
2
4
4.98
4.37
0.78
0.57
1.14
0.91
1
2
5
2
1
4
3
4
6
7.73
6.87
1.22
0.89
1.77
1.43
1
2
7
4
1
4
8
10.14
9.06
1.60
1.18
2.32
1.89
1
1
2
9
4
1
4
1
4
10
12.89
11.56
2.03
1.50
2.95
2.41
1
2
11
4
1
4
1
2
12
15.64
14.06
2.46
1.83
3.58
2.93
3
2
1
2
2
3
4
2
5.89
5.25
1.30
0.98
1.60
1.31
5
2
1
2
6
2
9.14
8.25
2.01
1.55
2.48
2.06
1
7
4
1
2
1
3
8
2
11.98
10.87
2.64
2.04
3.25
2.72
9
4
1
2
1
3
10
2
15.23
13.87
3.35
2.60
4.13
3.47
11
4
1
2
12
2
18.48
16.87
4.07
3.16
5.01
4.21
2
plywoods manufactured with waterproof glue can be satisfactorily used, but the industry
produces a particular type called
plyform
intended especially for formwork. It is this prod-
uct that is referred to in the remainder of this chapter.
Plyform is manufactured by gluing together an odd number of sheets of wood with
the grain of each sheet being perpendicular to the grain of the sheet adjoining it. The alter-
nating of the grains of the wood sheets, which is called
cross-banding
, greatly reduces the
shrinkage and warping of the resulting panels. It also results in a material whose adjacent
layers do not have the same properties (at least in a common direction). Consequently, the
section properties of plywood (such as moments of inertia and section moduli) are calcu-
lated using a transformed-area approach. Plyform can be obtained in thicknesses from
1
8
to
1
8
5
8
-
3
4
-in.
in. Actually, however, many suppliers only carry the
and
sizes, and the others
may have to be specially ordered.
The various types of wood used for manufacturing plywood (fir, spruce, larch, red-
wood, cedar, etc.) have different strengths and stiffnesses. Those types of woods having
