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

66 Chapter Four
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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
(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.
Recommended Maximum Pressures on Structural I Plyform—Values
in Pounds per Square Foot with Face Grain Parallel to Supports
TABLE 4-16
The allowable stresses are based on a load-duration less than 7 days
and moisture content less than 19%. The deflections are limited to l/360
with maxima not to exceed ¼ in. Spans are measured center to center
on the supports.
Use of Plywood for Curved Forms
Plywood is readily adaptable as form material where curved surfaces of
concrete are desired. Table 4-19 lists the minimum bending radii for millrun
Plyform panels of the thicknesses shown when bent dry. Shorter
radii can be developed by selecting panels that are free of knots or short
grain and by wetting or steaming the plywood prior to bending.
Hardboard
Tempered hardboard, which is sometimes used to line the inside surfaces
of forms, is manufactured from wood particles that are impregnated
with a special tempering liquid and then polymerized by baking.
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