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Truss Issues

  1. Nov 5, 2013 #1
    In the attached problem, I don't understand why members CD and DE are equal to 0. I was under the impression that the combined vertical components of BC and CD should equal 6+downward components of BC and EF, as to counteract the force straight down, but this is not the case.

    My questions:

    Why are the forces in members CD and DE equal to zero?

    If they are equal to 0, what stops the downward force from moving the structure?

    Thank you

    Note: G and Ay are 6 and 6, not 8 and 6 as shown. I used the right values for my calculations, but for some reason wrote 8 down
     

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    Last edited: Nov 5, 2013
  2. jcsd
  3. Nov 5, 2013 #2

    SteamKing

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    It's not clear from your post: Who is saying that members CD and DE are equal to 0? Are you talking about the forces in these members?
     
  4. Nov 5, 2013 #3
    Sorry yes - that's what I meant.
     
  5. Nov 6, 2013 #4

    SteamKing

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    You still haven't answered the main question: who is saying that the forces in members CD and DE are equal to 0?
     
  6. Nov 6, 2013 #5
    The answers in the back of the textbook
     
  7. Nov 6, 2013 #6
    IF THE STRUCTURE AND LOADING ARE BOTH SYMMETRICAL THEN THE EQUILIBRIUM OF JOINT d REQUIRES SYMMETRY OF FORCES IN cd AND de. tHAT IS THE CLUE....
     
  8. Nov 6, 2013 #7

    SteamKing

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    Hey, you don't have to shout.
     
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