Planks Joists
A floor system in a small building consists
of wood planks supported by 2-in. (nominal width)
joists spaced at distance s and measured from center
to center (see figure). The span length L of each
joist is 12 ft, the spacing s of the joists is 16 in., and
the allowable bending stress in the wood is 1250 psi.
The uniform floor load is 120 lb/ft2, which includes
an allowance for the weight of the floor system itself.
(a) Calculate the required section modulus S for the
joists, and then select a suitable joist size (surfaced
lumber) from Appendix G, assuming that
each joist may be represented as a simple beam
carrying a uniform load.
(b) What is the maximum floor load that can be
applied to your final beam selection in part (a)?
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