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Homework Help: Question about the location of max bending stress in a beam

  1. Nov 5, 2015 #1
    Hello guys,

    I have a simple question about the max bending stress in a beam.

    We know that in a cantilever beam, the biggest moment occurs at the wall. This is also the location of the max stress with equation stress= M*y/I
    , fig%201.jpg
    However, in a simple supported beam, we have

    This time, the max moment occurs at the middle of the beam. But I doubt this is the location of the max stress. I think the max stress location should still be at the wall.

    So we have a problem here: Is the max bending stress located at the location of the moment?

    Attached Files:

  2. jcsd
  3. Nov 5, 2015 #2


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    Staff Emeritus
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    In a simply supported beam, there is no 'wall' like there is for a cantilever beam.

    There's no problem here. Since σ = My / I, the location of max. bending stress is going to be where the max. bending moment is located.

    You have to pay attention to the support conditions for a beam because a simple support is not the same as a fixed support.
  4. Nov 6, 2015 #3
    Also, since a simply supported beam has zero slope at its center, from the center to each edge, each half of the beam looks like a cantilever beam.

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