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Homework Help: Structural Analysis Problem- internal hinge

  1. Sep 19, 2011 #1
    1. The problem statement, all variables and given/known data


    3. The attempt at a solution

    for part 1:

    i figured that this structure is not in static equilibrium. once load "P" is applied, the roller at "D" will function as a fulcrum and ABC will lift (make an angle with the horizontal).

    is that assumption correct?

    based on what i assumed:

    i assumed:

    2 reactions at "A", -Ax and -Ay
    0 reactions at B
    1 reaction at "D", Dy

    i summed the moments about "D"

    (clockwise moment is negative)


    Ay= -P/3L ========================

    Sum of forces in Y direction = 0:

    Ay+Dy-P= 0

    Dy= P-Ay

    after substituting for Ay:

    Dy=(3PL+P)/(3L) =========================

    i dont know how to find Ax.

    is what i did so far correct?

    help please
  2. jcsd
  3. Sep 20, 2011 #2


    User Avatar
    Science Advisor
    Homework Helper

    ride5150: That is currently incorrect. There is one reaction force at B, which is By. A roller symbol means a structure is constrained in the direction perpendicular to the roller, regardless whether the roller is in compression or tension. Hint 1: The moment at a frictionless hinge (point C) is always zero.
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