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

128 Chapter Five
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Equations for Calculating Allowable Span Lengths, in Inches, of Wood
Beams
Bending Deflection
Span
Condition
Bending l b
, in.
Shear l v
, in.
l D
, in. for
D = l/360
l D
, in. for
D = ¹⁄16 in.
Single
Spans
[96F b
S/w] 1/2
Eq. (5-30)
16F v
bd/w + 2d
Eq. (5-32)
[4,608EI/1,800/w] 1/3
Eq. (5-33a)
[4,608EI/80w] 1/4
Eq. (5-33b)
Multiple
Spans
[120F b
S/w] 1/2
Eq. (5-34)
192F v
bd/15w + 2d
Eq. (5-36)
[1,743EI/360w] 1/3
Eq. (5-37a)
[1,743EI/16w] 1/4
Eq. (5-37b)
Notes:
1. Physical properties of wood beams can be obtained from Table 4-1.
2. See Tables 4-2 and 4-3 for allowable stresses with adjustments from Tables 4-3a through 4-8.
3. Units for stresses and physical properties are in pounds and inches.
4. Units for w are lb per lin ft along the entire length of beam.
TABLE 5-3 Equations for Calculating Allowable Span Lengths, in Inches, for
Wood Beams based on Bending, Shear, and Deflection for Beams with Uniformly
Distributed Loads
Span
Condition
Single
Spans
Two
Spans
Three
or more
Spans
ww.EasyEngineering.n
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)
Notes:
1. See Tables 4-9 and 4-11 for physical properties of plywood and Plyform, respectively.
2. Reference Tables 4-10 and 4-12 for allowable stresses of plywood and Plyform, respectively.
3. Units for stresses and physical properties are in pounds and inches.
4. Units for w are lb per lin ft for a 12-in.-wide strip of plywood.
TABLE 5-4 Equations for Calculating Allowable Span Lengths, in Inches, for Plywood
and Plyform based on Bending, Shear, and Deflection due to Uniformly Distributed
Pressure
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