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

142 Chapter Five
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Deflection in Wales
Based on the deflection criterion of less than l/360, the span length of
the wales must not exceed the following calculated value:
From Eq. (5-37a), l ∆
= [1,743EI/360w] 1/3
= [1,743(1,600,000)(10.72)/360(1,650)] 1/3
= 36.9 in.
Based on a deflection criterion of less than ¹⁄16 in., the span length
of the wales must not exceed the following calculated value:
From Eq. (5-37b), l ∆
= [1,743EI/16w] 1/4
ww.EasyEngineering.n
= [1,743(1,600,000)(10.72)/16(1,650)] 1/4
= 32.9 in.
Summary for the Double 2 ë 4 Wales
For bending, the maximum span length of wales = 28.8 in.
For shear, the maximum span length of wales = 24.7 in.
For deflection, the maximum span length of wales = 32.6 in.
For this design, shear governs the maximum span length of the
wales. Because the wales are supported by the ties, the spacing of the ties
must not exceed 24.7 in. However, the ties must have adequate strength
to support the load from the wales. For uniformity and constructability,
choose a maximum span length of 24 in. for wales and determine the
required strength of the ties to support the wales.
Strength Required of Ties
Based on the strength of the wales in bending, shear, and deflection,
the wales must be supported every 24 in. by a tie. A tie must resist the
concrete pressure that acts over an area consisting of the spacing of
the wales and the span length of the wales, 24 in. by 24 in., or 2 ft by
2 ft. The load on a tie can be calculated as follows:
Area = 2.0 ft × 2.0 ft
= 4.0 sq ft
Tie tension load = 825 lb per sq ft (4.0 sq ft)
= 3,300 lb
The ties for the wall must have a safe tension load of 3,300 lb. A
standard-strength 3,000-lb working load tie is not adequate. Therefore
a heavy-duty 4,000-lb working load tie is required.
An alternative method is to select a 3,000-lb tie and calculate the
allowable spacing of the ties to support the wale. For a 24 in., or 2.0 ft,
spacing of wales, the equivalent uniformly distributed load along a
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