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Zero-force member problem (Statics)

  1. Mar 25, 2013 #1
    1. The problem statement, all variables and given/known data
    Determine the zero force members in the following truss

    2. Relevant equations

    - If only two members meet in an unloaded joint, both are zero-force members.
    - If three members meet in an unloaded joint of which two are in a direct line with one another, then the third member is a zero-force member.

    - If two members meet in a loaded joint and the line of action of the load coincides with one of the members, the other member is a zero-force member.

    3. The attempt at a solution

    Ok, I got 6 (there are 8 according to the solution) using the above rules:
    HF, HI, OQ, QR, BC, and DE

    The solution says that BE and LJ are also zero force members, but I have no clue why...

    Any help please?

    Thanks in advance!

    Attached Files:

  2. jcsd
  3. Mar 25, 2013 #2


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    Not LJ, its IJ, why? If BC is a zero force member, that should tell you something about BE (and DE).
  4. Mar 26, 2013 #3
    Ok, I had thought about IJ before but since the solution didn't mention it I didn't count it...

    Now, for BE: since BC is a zero-force member, can we "ignore" it and then consider the other 3 with Rule #2?
  5. Mar 26, 2013 #4


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  6. Mar 26, 2013 #5
    Thank you sir ;)
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