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

226 Chapter Nine
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the full height of the wall, the design should be based on continuous
beam action for the studs. The allowable span length of studs, the
distance between wales, based on bending can be calculated from Eq.
(5-34) in Table 9-5 as follows:
From Eq. (5-34): l b
= [120F b
S/w] 1/2
= [120(1,875)(3.06)/713] 1/2
= 31.1 in.
Shear in 2 ë 4 S4S Studs
The allowable span length based on shear in the studs can be calculated
from Eq. (5-36) in Table 9-5 as follows:
ww.EasyEngineering.n
From Eq. (5-36) l v
= 192F v
bd/15w + 2d
= 192(218)(1.5)(3.5)/15(713) + 2(3.5)
= 27.5 in.
Deflection in 2 ë 4 S4S Studs
The permissible deflection is l/360, but not greater than ¹⁄16 in. Using
Eqs. (5-37a) and (5-37b) from Table 9-5, the allowable span lengths
due to deflection can be calculated as follows:
From Eq. (5-37a): l ∆
= [1,743EI/360w] 1/3 for ∆=l/360
= 1,743(1,600,000)(5.36)/360(713)] 1/3
= 38.8 in.
From Eq. (5-37b): l ∆
= [1,743EI/16 5 ⁄8 w] 1/4 for ∆=¹⁄16 in.
= [1,743(1,600,000)(5.36)/16(713)] 1/4
= 33.8 in.
Summary for 2 ë 4 S4S Studs
For bending, the maximum span length of studs = 31.1 in.
For shear, the maximum span length of studs = 27.5 in.
For deflection, the maximum span length of studs = 33.8 in.
For this design, bending governs the maximum span length of the
studs. Because the wales must support the studs, the maximum spacing
of the wales must be no greater than 27.5 in. For constructability and
ease of fabrication, it is desirable to space the studs 24 in. apart, center to
center. This will allow easier fabrication of the forms because the 24 in.
spacing will easily match the 8-ft-length of the plywood panels.
Bearing Strength between Studs and Wale
For this design, double wales will be used. Wales for wall forms of
this size are frequently made of two-member lumber whose nominal
thickness is 2 in., separated by short pieces of 1-in.-thick blocks.
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