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Truss (statics)

  1. Feb 14, 2007 #1
    1. The problem statement, all variables and given/known data

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    2. Relevant equations

    3. The attempt at a solution

    Im not really sure how to get started. I understand the method of Joints, and all the solved examples I can follow. I started by analyzing the support reactions, and I am stuck already. There is the force [tex]P_2[/tex], and then there are going to be the following forces: [tex] G_x, G_y, A_x, A_y[/tex]?

    Any advice on how to start this problem would be appreciated.

    Attached Files:

  2. jcsd
  3. Feb 14, 2007 #2


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    Actually, one of the supports should be a roller support, since I assume this is supposed to be a statically determinate system.

    Hint: after analyzing the supports, which one is equivalent to a roller support, i.e. which one has only the horizontal component of the reaction?
    Last edited: Feb 14, 2007
  4. Feb 14, 2007 #3


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    Staff: Mentor

    There are two pin joints (no moment), and the far right side is free.
  5. Feb 14, 2007 #4
    Im gonna guess that G can be considered a roller?
  6. Feb 14, 2007 #5
    And since the far right side is free, what does this tell me?
  7. Feb 14, 2007 #6


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    That condition is not needed in order for the truss to be statically determinate.

    Remember in order for a truss to be statically determinate the number of bars (each carries a force) + the number of reactions must be equal to twice the number of joints (2 equations of equilibrium for each joint).

    In this case, there are 10 bars, and 4 reactions, and 7 joints. This truss is statically determinate.

    I would solve it by using the section method and start by cutting the members BC, FC and EF.

    supenc3. are you familiar with zero force members? that's what astronuc is implying. Note that if you use the joint method at D, and sum forces on y, you will get that DC must be a zero force member.
    Last edited: Feb 14, 2007
  8. Feb 15, 2007 #7
    No, Im not really familiar with Zero Force members, but it is my book so Il try to look over it. Il go and try it again...Thanks
  9. Feb 15, 2007 #8


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    I know, I actually went wrong about the roller support fact; if it was a roller support, it would be a mechanism.

    Edit: I dislike sketches of this kind, since for some reason, they tend to confuse me.
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