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

108 Chapter Five
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For this beam, the physical properties are:
l= 96 in.
= 1,600,000 lb per sq in.
I= bd 3 /12 = [1.5 in. × (7.25 in.) 3 ]/12
= 20.8 in. 4
Substituting these values into Eq. (5-23) gives:
∆= 19Pl 3 /384EI
= [19(190 lb)(96 in.) 3 ]/[384(1,600,000 lb per sq in.)(20.8 in. 4 )]
= 0.25 in.
Suppose the maximum permissible deflection is l/360. The permissible
deflection would be 96/360 = 0.27 in., which is larger than
the calculated deflection of 0.25 in. Therefore, the 2 × 6 beam is adequate
for deflection.
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Multiple-Span Beam with Concentrated Loads
Figure 5-7 illustrates a beam, such as a wale, that is continuous over
several supports, the form ties, with equally spaced concentrated loads
acting on it. The concentrated loads act on the wale through the studs.
The same loading condition will exist where floor decking is supported
on joists, which in turn are supported by stringers, and where the
stringers are supported by vertical shores. For this type of loading, the
positions of the concentrated loads P can vary considerably, which will
result in some rather complicated calculations to determine the maximum
deflection. If the concentrated loads are transformed into a uniformly
distributed load, having the same total value as the sum of the
FIGURE 5-7 Concentrated loads on a beam.
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