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How to calculate tension/compression in a truss bridge (diagram shown)?

  1. Nov 29, 2009 #1
    In general, in a truss diagram the forces like load, reaction force are act on joints but in this case the load is in the middle of two joints. How can I find forces on members in this case?

    9qfdw6.jpg

    Your help is really appreciated. Thank you for reading
     
  2. jcsd
  3. Nov 29, 2009 #2

    Mech_Engineer

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    Since the force is in the center of the spar, you could split it into 2 5N forces at its ends...
     
  4. Nov 29, 2009 #3
    Could you help me find out what force (tension/compression) do the truss members have please? I have done most of them but the middle section with "X" trusses are making it dificult to calculate the forces the carry....
     
  5. Nov 29, 2009 #4
    346oy09.jpg
    I have done some calculations to find out the forces but i am confused with the middle section. Can someone tell me if figure 2 is correct or not?


    Thank you
     
    Last edited: Nov 29, 2009
  6. Nov 30, 2009 #5

    Mech_Engineer

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    You can just assume one or the other (tension or compresison) and if you guessed wrong, you will get a negative value.
     
  7. Dec 8, 2009 #6
    Well, you can't use method of sections for the center.... you'd have to use method of joints and treat that "external load" as a moment on the joint you're analyzing that's "connected" to the member that's loaded (as well as in force equilibrium)........ seems as if the only two joints you'd concern yourself with with that center load are the ones to the left and right of it. at least that's how id attempt to do it. start at the supports and move your way towards the center.
     
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