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Determining a zero force member visually

  1. Sep 25, 2013 #1
    Hello,

    When given a truss structure, how does one tell visually just by looking at the structure which members are zero force members?
     
  2. jcsd
  3. Sep 25, 2013 #2

    PhanthomJay

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    From Wiki:

    • "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."


    An unloaded joint is a joint where no external forces are applied , or a joint where there is no external reaction force.

    A loaded joint is a joint where external forces are applied , or a joint where there is an external reaction force.
     
  4. Sep 25, 2013 #3

    nvn

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    Woopydalan: See also post 2345373.
     
  5. Oct 20, 2013 #4
    So that means if you have 4 members at a joint, then none of the members can be zero force members? I am looking at a homework problem and this is the case where 4 members meet and yet one or more of the members is a zero force member. I thought it was only 3 members meeting
     
  6. Oct 20, 2013 #5

    AlephZero

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    No, it just means you can't decide if they are zero force members by looking at that joint. But the other end of each member is connected to a different joint, and that joint might tell you it is a zero force member.

    Of course it is also possible for a member in a complicated structure to have zero force just by happenstance, but that's not very interesting.
     
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