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Homework Help: Castiglianos second theorem for indeterminate structures

  1. Mar 8, 2010 #1
    in the following question it is known that the rod BD has only axial internal forces, (which i called Q) if AL2=10*I, find the reaction at C and the internal force Q.
    Assume that the energy of normal forces is negligible compared to moment where there are both.

    instead of using L/4 i defined L/4=a

    the correct answers are supposed to be Cy=0.346P and Q=0.042P

    these are my calculations

    i have tried solving it 4 times now and cant get the correct answer.
  2. jcsd
  3. Mar 8, 2010 #2
    the structure is twice statically indeterminate therefore i need to use 2 equations to find the 2 unknowns
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