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Homework Help: I beam stress

  1. Feb 8, 2013 #1
    A uniform simply supported beam, 5 m long and having a cross-section as shown, is to support a load which varies linearly from zero at the left hand support to a magnitude of 20 kN/m at the right hand support. Determine the position and magnitude of the maximum bending stress.
    ANS : 140 MPa, 2.89 m from left

    Total load w*L/2 = 50,000
    Load at distance x (w*x)/L

    I know that distance of maximum load = L/sqrt3 = 2.89

    So the maximum bending moment = (20,000*2.89)/5 = 11560

    I have out this into the formula M*Y/I =σ but get an incorrect answer

    Unfortunately the picture with dimensions is unable to upload but it is an I beam with a second moment of area as 0.00003813 and a distance from the neutral axis as 0.1

  2. jcsd
  3. Feb 8, 2013 #2


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    It would be nice to know what your incorrect answer was.
  4. Feb 8, 2013 #3


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    I agree with the 2.89 but not the 11560 (I get 32075). What's the rationale for that equation?
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