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Homework Help: Determine the shear stress

  1. Jul 1, 2013 #1
    1. The problem statement, all variables and given/known data

    Determine the shear stress, [itex]\tau[/itex]E, at point E that corresponds to the maximum shear force along the length of the beam. V = 25kN

    b= 55 mm
    c=150 mm
    d=110 mm
    e=65 mm

    2. Relevant equations

    [itex]\tau[/itex]E = [itex]\frac{V*Q}{I*t}[/itex]

    Q = [itex]\bar{y}[/itex]'*A'

    3. The attempt at a solution

    I was able to find the shear stress for point D, but I'm having trouble finding point E. How do I find Q for that point? I read an example in my textbook but there was not much of an explanation.

    Is point E the centroid for the area when the neutral axis is at point D? If this is the case, I would be able to find the shear stress.

    Attached Files:

  2. jcsd
  3. Jul 1, 2013 #2


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    Unfortunately, the diagram is not clear on where point E is located. The shear stress in the beam takes a large jump at the intersection of the upper flange and the web of the beam. In any case, Q will be the first moment of the area between E and the top of the flange, referenced about the neutral axis.
  4. Jul 7, 2013 #3


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    I am not sure, since I did not try it.

    Technically speaking, we could say point E is located at a distance 0.80*b from the top edge of the upper flange. I.e., point E is located at (0.50*c + 0.20*b) from point D. Therefore, based on this assumption, you could find the shear stress at point E.
  5. Jul 8, 2013 #4
    Thanks for all of the input. I was told to assume that point E was located at the point where the web meets the flange. Great drawing!!(sarcasm) Got this one wrong.
  6. Jul 9, 2013 #5
    Glad you are sorted now. However, shear stress is not evaluated at a point, but at a section. There is a difference.
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