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

446 Chapter Sixteen
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For a deflection less than l/270, substituting 270 for 360 in Eq. (5-57a) of
Table 5-4:
l d
= [1,743EI/270w s
] 1/3
= [1,743(1,650,000)(0.296)/270(225)] 1/3
= 24.1 in.
For deflection not to exceed ¼ in., substituting ¼ in. for ¹⁄16 in., Eq.
(5-57b) of Table 5-4:
l d
= [1,743EI/4w s
] 1/4
= [1,743(1,650,000)(0.296)/4(225)] 1/4
ww.EasyEngineering.n
= 31.1 in.
Below is a summary of the allowable span lengths of the 7 ⁄8-in. Class I
Plyform decking:
For bending, the maximum allowable span length = 24.5 in.
For shear, the maximum allowable span length = 54.7 in.
For deflection, the maximum allowable span length = 24.1 in.
For this example, the spacing of the wood joists must not exceed
the maximum allowable span length of the Plyform decking, which is
24.1 in. Thus, the proposed 24-in. spacing of the wood joists with 7 ⁄8-in.
Class I Plyform decking is satisfactory.
Deck Forms Supported by Tubular Steel Scaffolding
Where ground conditions under a bridge deck permit the use of tubular
steel scaffolding, this method of supporting the formwork can be
satisfactory and economical, as illustrated in Figure 16-8.
FIGURE 16-8 Deck forms supported by tubular steel scaffolding. (Source: Patent
Construction Systems)
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