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Distributed load

  1. Jul 7, 2016 #1
    1. The problem statement, all variables and given/known data
    why the force of distributed act upward?
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    RBSaoNE.jpg
    2. Relevant equations


    3. The attempt at a solution
    why shouldnt it act downward due to gravity pull?
     
  2. jcsd
  3. Jul 8, 2016 #2

    SteamKing

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    If you read the text in the book, the author has chosen to show the loads acting in their positive direction. which is why F is pointing up rather than down, like a gravity load.
     
  4. Jul 8, 2016 #3

    Delta²

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    What do you think would change in the equations if you take the load to act downwards?

    As long as you keep stable the sign conventions through the whole derivation, nothing changes in the equations.
     
    Last edited: Jul 8, 2016
  5. Jul 10, 2016 #4
    You may be assuming that the distributed load is against gravity. This problem could be a model of a structural member such as a window mullion carrying a distributed wind load, where gravity is a force along the axis of the member.
     
  6. Jul 10, 2016 #5
    Do you mean the author assume the beam carrying win load , so the forces act upwards?
     
  7. Jul 10, 2016 #6
    I don't know what the author assumed. I am just indicating that you have made an assumption that the distributed load is acting vertically, when it might just be acting horizontally if you regard the diagram (a) given as a plan., rather than as an elevation. All this doesn't affect the calculations, but helps you understand a possible application of the mechanics that does occur in everyday engineering practice.
     
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