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Homework Help: Too close to maximum deflection or not too close to maximum deflection

  1. Mar 17, 2010 #1
    1. The problem statement, all variables and given/known data
    Calculating uniform and sometimes point loads on simple beams and the calculated beam deflections using ETLs (estimated tabular loads).

    My question in simply if I have found a deflection that is .005" less than the given maximum deflection, is it so close that if I don't recalculate, will my professor think that I'm some kind of an engineering maverick/loose cannon? I'm not kidding, I seriously just don't want to be too close for comfort, and I don't know yet how close structural engineers like to get.

    2. Relevant equations
    ETL = [(M)(8)] / L

    deflection = [(5)(ETL)(L3) / [(384)(E)(I)]

    3. The attempt at a solution

    Deflection found. too close?

    actual deflection = .660" maximum deflection = .6666"
  2. jcsd
  3. Mar 17, 2010 #2


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    If that is the maximum great, don't worry it is just fine, safety factors are still there.
  4. Mar 17, 2010 #3
    thanks, Lok!
  5. Mar 20, 2010 #4
    Just to put a perspective: A frame manufacturer I know tested a bare frame and got pretty much the calculated deflection. Then the other frames adjacent were built, and connected with purlins etc. Same test on original frame got about two thirds of the original deflection. Finally all the sheet cladding was added. Tested again, the deflection was about one third of the calculated deflection.
  6. Mar 22, 2010 #5
    That makes sense, I'm so glad. I turn in my final project tomorrow!
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