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

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Forms for Beams and Floor Slabs 329
Plywood
Thickness,
in.
¹ 5 ⁄32 1,970
(1,970)
½ 2,230
(2,230)
¹ 9 ⁄32 2,300
(2,300)
5
⁄8 2,515
(2,515)
23
⁄32 3,095
(3,095)
¾ 3,315
(3,315)
1 1 ⁄8 6,860
(6,860)
Support Spacing, in.
4 8 12 16 20 24
470
(530)
605
(645)
640
(720)
800
(865)
1,190
(1,190)
1,275
(1,275)
2,640
(2,640)
130
(175)
175
(230)
195
(260)
250
(330)
440
(545)
545
(675)
1,635
(1,635)
—
—
—
—
—
(110)
105
(140)
190
(255)
240
(315)
850
(995)
—
—
—
—
—
—
—
(100)
135
(170)
170
(210)
555
(555)
—
—
—
—
—
—
—
—
—
—
—
(115)
340
(355)
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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 11-5 Recommended Maximum Pressures on Structural I Plyform—Values
in Pounds per Square Foot with Face Grain Parallel to Supports
The joists must have adequate strength and rigidity to resist
bending stresses, shear stresses, and deflection between supports. The
equations for determining the allowable span lengths of wood members
were presented in Chapter 5 and are reproduced in Table 11-6 for
clarity. The allowable stresses for bending F b
and shear F v
are in pounds
Bending Deflection
Span
Condition
Bending
l b
, in.
Shear l v
, in.
l D
, in. for
∆ = l/360
l D
, in. for
∆ = 1 ⁄ 16 in.
Single
spans
[96F b
S/w] 1/2
Eq. (5-30)
16F v
bd/w + 2d
Eq. (5-32)
[4,608EI/1,800w] 1/3
Eq. (5-33a)
[4,608EI/80w] 1/4
Eq. (5-33b)
TABLE 11-6 Equations for Calculating Allowable Span Lengths for Single-Span
Wood Beams Based on Bending, Shear, and Deflection for Beams with Uniformly
Distributed Loads, in.
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