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Homework Help: Design of floor joists in a domestic building

  1. Jul 31, 2008 #1
    Could i have some help with the following:

    Design, floor joists in a domestic building to span between walls 3.0m apart.

    the construction of the floor is
    18mm timber boards
    15mm overall plasterboard + skim coat

    The joists are 50mm wide and at 450mm centres
    The permissible stress in the timber is 5.3N/mm(squared) and the elstic modulus of the timber is 8000N/mm(squared)
    the deflection must be limited at 0.3% of the span.
  2. jcsd
  3. Jul 31, 2008 #2


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    Staff: Mentor

    What is your background? What city is this in? What are the local codes regarding this kind of construction? You need a licensed engineer to make those calculations for you -- one who is familiar with your municipality's building codes and inspectors.
  4. Aug 1, 2008 #3


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    Science Advisor

    Is this homework? If not, there's not much of a chance for getting an accurate result without knowing local building codes.
  5. Aug 1, 2008 #4


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    Staff: Mentor

    Even if we had a PE structural engineer as a member or on staff, we wouldn't condone giving such advice since we can't be sure this isn't a code violation (a homeowner trying to do his own structural engineering).
  6. Aug 3, 2008 #5
    Thanks for getting back to me this is actually a college assignment that ive been stuck on for quite a while that i needed help on for designing the floor joists.
  7. Aug 3, 2008 #6


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    Homework Helper

    Ok so is a college assignment. Start off by showing your work, so we can know with what you are having problems.
  8. Aug 4, 2008 #7


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    Science Advisor
    Homework Helper

    john paul jr: Do you have the density of the timber boards, and of the joist material? Do you have the density of plasterboard? Do you have the floor applied live load per unit area?
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