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

234 Chapter Nine
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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
Support Spacing, in.
4 8 12 16 20 24
(3,095)
470
(530)
605
(645)
640
(720)
800
(865)
1,190
(1,190)
130
(175)
175
(230)
195
(260)
250
(330)
440
(545)
—
—
—
—
—
(110)
ww.EasyEngineering.n
¾ 3,315
(3,315)
1,275
(1,275)
545
(675)
105
(140)
190
(255)
240
(315)
—
—
—
—
—
—
—
(100)
135
(170)
170
(210)
—
—
—
—
—
—
—
—
—
—
—
(115)
1 1 ⁄8 6,860 2,640 1,635 850 555 340
(6,860) (2,640) (1,635) (995) (555) (355)
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.
Recommended Maximum Pressures on Structural I Plyform—Values
in Pounds per Square Foot with Face Grain Parallel to Supports
TABLE 9-10
Allowable Pressure Based on Bending Deflection
For pressure controlled by bending deflection, Eqs. ( 9-3) and (9-4),
w d
= 2220EI∆ b
/(l s
) 4 for two spans (9-3)
w d
= 1743EI∆ b
/(l s
) 4 for three or more spans (9-4)
where ∆ b
= permissible deflection of plywood, in.
w d
= uniform pressure of concrete, lb per sq ft
l s
= clear span of plywood plus ¼ in. for 2-in. supports, and
clear span plus 5 ⁄8 in. for 4-in. supports, in.
E = modulus of elasticity of plywood, lb per sq in.
I = moment of inertia of a plywood strip 12 in. wide, in. 4 /ft
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