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

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Forms for Columns 295
For shear, from Eq. (10-4),
l v
= 192F v
bd/15w + 2d
= 192(218.7)(3.5)(1.5)/15(1,172) + 2(1.5)
= 15.5 in.
For deflection not to exceed l/360, from Eq. (10-5),
l ∆
= [1,743EI/360w] 1/3
= [1,743(1,600,000)(0.984)/360(1,172)] 1/3
= 18.6 in.
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For deflection not to exceed ¹⁄16 in., from Eq. (10-6),
l ∆
= [1,743EI/16w] 1/4
= [1,743(1,600,000)(0.984)/16(1,172)] 1/4
= 19.6 in.
Below is a summary of the allowable span lengths of the 2 × 4
vertical wood battens:
For bending, the maximum span length = 16.6 in.
For shear, the maximum span length = 15.5 in.
For deflection, the maximum span length = 18.6 in.
For this example, shear governs the maximum span length of the
wood battens. The spacing of the column clamps at the bottom of the
form must not exceed 15.5 in. For constructability, the spacing would
likely be placed at 12 in. Figure 10-4 shows a plan view of the assembled
forms.
The pressure on the forms is greatest at the bottom, linearly
decreasing to zero at the top of the form, see Eq. (10-1). Therefore, the
spacing of the column clamps may be increased in the upper portion
of the forms. It may be desirable to place the Plyform panel in the
horizontal direction at the bottom of the form, and then place the
panels in the vertical direction in the upper portion of the form where
the concrete pressure is not as great. The procedure illustrated in this
example may be used to calculate the allowable spacing of column
clamps at any height of the column forms, based on the strength and
deflection of the sheathing.
The column clamps must be strong enough to resist the loads
transmitted to them by the sheathing. There are numerous manufacturers
of patented column clamps for forming concrete columns.
These manufacturers generally specify the safe spacing for their particular
clamps. The following sections provide information on patented
clamps.
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