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

294 Chapter Ten
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(strong direction) across wood battens. Therefore, the Plyform sheathing
selected for this application will be satisfactory. The length of the
Plyform for one side of the column form will be 20.75 in., as shown in
Figure 10-3.
From Tables 4-2, 4-4, and 4-7 the allowable stresses for the No. 2
grade Southern Pine 2 × 4 vertical wood battens laid flat and shortduration
loading can be calculated as follows:
Allowable bending stress, F b
= C D
× C fu
× (reference design
bending value)
= (1.25) × (1.1) × (1,500 lb per sq in.)
= 2,062.5 lb per sq in.
Allowable shear stress, F v
= C D
× (reference design shear value)
= (1.25) × (175 lb per sq in.)
= 218.7 lb per sq in.
Modulus of elasticity, E = 1,600,000 lb per sq in.
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The three vertical wood battens must transfer the concrete
pressure between column clamps. The center batten is the most
heavily loaded and must sustain the pressure to the midpoint of
the adjacent battens, a distance of 9.375 in. The uniform load
between column clamps on the center batten may be calculated as
follows:
w = (1,500 lb per sq ft) (9.375/12 ft)
= 1,172 lb per lin ft
The physical properties of section modulus and moment of inertia
of the 2 × 4 wood battens laid flat can be obtained from Table 4-1
as follows:
From Table 4-1:
Section modulus, S = 1.313 in. 3
Moment of inertia, I = 0.984 in. 4
Neglecting any contribution of the plywood for transferring the concrete
pressure between supports, the allowable span length of the 2 × 4
wood battens based on bending, shear, and deflection may be calculated
as follows:
For bending, from Eq. (10-3),
l b
= [120F b
S/w] 1/2
= [120(2,062.5)(1.313)/1,172] 1/2
= 16.6 in.
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