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Shear Stress in Beams - Full Working, getting wrong

  1. Jan 5, 2016 #1
    Hi,

    I'm doing question (c)(ii) in the image below, full working is provided below:

    (c)(i) is 150kPa.

    I = bh^3/12 - 2 * bh^3/12
    (0.25 * 0.256^3)/12 - (2* (0.119 * 0.22^3)/12)
    = 1.3831 x 10^-4 m^4

    Q = y*A
    = 0.119 * 0.018 * 0.250
    = 5.355 x 10^-4 m^3

    shear force = (150000 * 5.355 x 10^-4)/(1.3831 x 10^-4 * 0.25)
    = 2.32 MPa

    I know that the solution is shear force minimum = 48.4 MPa.

    Where have I gone wrong?

    Thanks!

    tH66f.jpg
     
  2. jcsd
  3. Jan 5, 2016 #2

    PhanthomJay

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    looks like you used the wrong thickness when calculating the min shear stress in the web (you used the flange width in error)
     
  4. Jan 5, 2016 #3
    That's it, thanks.
     
  5. Jan 5, 2016 #4

    SteamKing

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    Shear force is not measured in Pascals. It is measured in Newtons.
    You're supposed to be calculating shear stress here.
     
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