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

202 Chapter Eight
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Deflection in the double plates for ∆ =l/360:
Equation (5-37a), l ∆
= [1,743EI/360w] 1/3
= [1,743(1,600,000)(10.72)/360(600)] 1/3
= 51.7 in.
Deflection in the double plates for ∆ =¹⁄16 in.:
Equation (5-37b), l ∆
= [1,743EI/80w] 1/4
= [1,743(1,600,000)(10.72)/16(600)] 1/4
= 42.0 in.
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Summary for Double 2 ë 4 Plates
For bending, maximum span length = 45.4 in.
For shear, maximum span length = 57.4 in.
For deflection, maximum span length = 42.0 in.
The maximum permissible span length of the double plates is
governed by deflection at 42.0 in. For constructability, choose a spacing
for the form ties at 36 in.
Check the strength of the tie based on the concrete pressure area
of 24 in. by 36 in. The load on a tie can be calculated as follows:
Area = 2.0 ft × 3.0 ft
= 6.0 sq ft
Tie tension load = 600 lb per sq ft (6.0 sq ft)
= 3,600 lb
The ties for the wall must have a safe tension load of 3,300 lb.
Therefore, use a 4,000-lb working load tie. This panel will weigh
approximately 100 lb. Although this panel was designed by using
equations to illustrate the methods, it could have been designed more
quickly by using the information given in the tables for the design of
plywood or Plyform.
Procedure for Erection of Forms for Footings
Figure 8-3 will be used to illustrate and describe the step-by-step procedure
for erecting wall forms using these panels. At the time the wall
footing was poured, short pieces of lumber were set in the concrete
flush with the top surface of the footing at about 4-ft intervals to serve
as nailer inserts. The procedure in erecting the forms is as follows:
1. Place two rows of plywood-faced 4 × 4 S4S lumber, with the
inner faces separated by the thickness of the wall, along the
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