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Homework Help: How do I find the critical value of shear stress?

  1. Apr 21, 2015 #1
    1. The problem statement, all variables and given/known data
    Finding the critical value of shear stress at the junction and at the neutral axis

    2. Relevant equations
    stress max = (Bending moment x height from neutral axis)/Moment of inertia
    Shear stress = Shear force/area

    3. The attempt at a solution
    I am able to do the first 2 parts but not the last one. I'm not really sure which of the 2 equations to use and what it meant by critical value.

    Attached Files:

  2. jcsd
  3. Apr 21, 2015 #2


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    Staff Emeritus
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    Homework Helper

    You are not going to be able to calculate any meaningful shear stresses with the formula:

    Shear stress = Shear force/area

    This formula:

    stress max = (Bending moment x height from neutral axis)/Moment of inertia

    is not for the maximum stress. It is the general formula for calculating only the bending stress, which may or may not necessarily be the maximum stress.

    For this type of section, the shear stress is zero at the outer fibers of the flanges and a maximum at the N.A.

    At points where there is a change in the distribution of material, at the junction of the flanges with the web, there is a drastic change in shear stress.

    Find a better formula for shear stress and you'll have better success analyzing this problem.
  4. Apr 21, 2015 #3
    Do you know the shear flow formula?
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