Formwork for Concrete Structures by R.L.Peurifoy and G.D- By EasyEngineering.net

326 Chapter Eleven
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Plywood
Thickness,
in.
¹ 5 ⁄32 2,715
(2,715)
½ 2,945
(2,945)
¹ 9 ⁄32 3,110
(3,110)
5
⁄8 3,270
(3,270)
23
⁄32 4,010
(4,010)
¾ 4,110
(4,110)
1 1 ⁄8 5,965
(5,965)
Support Spacing, in.
4 8 12 16 20 24 32
885
(885)
970
(970)
1,195
(1,195)
1,260
(1,260)
1,540
(1,540)
1,580
(1,580)
2,295
(2,295)
355
(395)
405
(430)
540
(540)
575
(575)
695
(695)
730
(730)
1,370
(1,370)
150
(200)
175
(230)
245
(305)
265
(325)
345
(325)
370
(410)
740
(770)
—
115
100
(135)
145
(190)
160
(210)
210
(270)
225
(285)
485
(535)
—
—
—
—
—
(100)
—
(100)
110
(145)
120
(160)
275
(340)
—
—
—
—
—
—
—
—
—
—
—
—
130
(170)
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Notes:
1. Courtesy APA—The Engineered Wood Association, “Concrete Forming,” 2004.
2. Deflection limited to l/360th of the span, l/270th for values in parentheses.
3. Plywood continuous across two or more spans.
TABLE 11-2 Recommended Maximum Pressure on Plyform Class I—Values in
Pounds per Square Foot with Face Grain Across Supports
use the clear span between the supports plus ¼ in. for supports whose
nominal thickness is 2 in., and the clear span between the supports
plus 5 ⁄8 in. for supports whose nominal thickness is 4 in.
The recommended concrete pressures are influenced by the number
of continuous spans. For face grain across supports, assume three
continuous spans up to 32-in. support spacing and two spans for
greater spacing. For face grain parallel to supports, assume three
spans up to 16 in. and two spans for 20 and 24 in. These are general
rules as recommended by APA—The Engineered Wood Association.
There are many combinations of frame spacings and plywood
thicknesses that may meet the structural requirements for a particular
job. However, it is recommended that only one thickness of plywood
be used and then the frame spacing varied for different pressures. Plyform
can be manufactured in various thicknesses, but it is good practice
to base design on ¹ 9 ⁄32, 5 ⁄8, 23 ⁄32, and ¾-inch Class I Plyform because
they are the most commonly available thicknesses.
Tables 11-2 through 11-5 give the recommended maximum pressures
of concrete on Class I and Structural I Plyform decking. Calculations for
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