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

220 Chapter Nine
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Span
Condition
Single
Spans
Two
Spans
Three
or more
Spans
Equations for Calculating Allowable Span Lengths, in Inches, for Plywood
and Plyform
Bending l b
, in.
[96F b
S e
/w b
] 1/2
Eq. (5-40)
[96F b
S e
/w b
] 1/2
Eq. (5-40)
[120F b
S e
/w b
] 1/2
Eq. (5-41)
Shear l s
, in.
24F s
(Ib/Q)/w s
Eq. (5-46)
19.2F s
(Ib/Q)/w s
Eq. (5-47)
20F s
(Ib/Q)/w s
Eq. (5-48)
Bending Deflection
l d
, in. for
∆ = l/360
⎡921.6EI
⎤
⎢
⎣ 360w ⎥
d ⎦
Eq. (5-55a)
⎡2,
220EI
⎤
⎢
⎣ 360w ⎥
d ⎦
Eq. (5-56a)
⎡1,
743EI
⎤
⎢
⎣ 360w ⎥
d ⎦
Eq. (5-57a)
1/
3
1/
3
1/
3
l d
, in. for
∆ = 1/16 in.
⎡921.6EI
⎤
⎢
⎣ 16w ⎥
d ⎦
Eq. (5-55b)
⎡2,
220EI
⎤
⎢
⎣ 16w ⎥
d ⎦
Eq. (5-56b)
⎡1,
743EI
⎤
⎢
⎣ 16w ⎥
d ⎦
Eq. (5-57b)
1/
4
1/
4
1/
4
Shear
Deflection
l s
, in. for
∆ = l/360
1, 270EI
e
2
6 wCt
s
3 0
Eq. (5-60a)
1, 270EI
e
2
6 wCt
s
3 0
Eq. (5-60a)
1, 270EI
e
2
6 wCt
s
3 0
Eq. (5-60a)
ww.EasyEngineering.n
Notes:
1. See Table 9-3 for physical properties of Plyform.
2. Refer Table 9-4 for allowable stresses of Plyform.
3. Units for stresses and physical properties are in pounds and inches.
4. Units for w are lb per lineal foot for a 12-in.-wide strip of Plyform.
TABLE 9-6 Equations for Calculating Allowable Span Lengths, in Inches, for Plywood
and Plyform Based on Bending, Shear, and Deflection due to Uniformly Distributed
Pressure
Design of Forms for a Concrete Wall
The use of the equations and principles developed in Chapter 5 will
be illustrated by designing the forms for a concrete wall. The design
will include the sheathing, studs, wales, and form ties.
In the design of wall forms, the thickness and grade of the plywood
is often selected based on availability of materials. For this
design example, a ¾-in.-thick Plyform Class I has been selected. The
lumber will be No. 2 grade S4S Southern Pine with no splits. The
following design criteria will apply:
1. Height of wall, 10 ft 0 in.
2. Rate of filling forms, 5 ft per hr.
3. Temperature, 80°F.
4. Concrete unit weight, 150 lb per cu ft.
5. Type I cement will be used without retarders.
6. A dry condition for wood, less than 19% moisture content.
7. Short load duration, less than 7 days.
8. Limit deflection to l/360, but no greater than ¹⁄16 in.
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