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Homework Help: Find forces acting on a combined beam with load.

  1. Feb 12, 2013 #1
    I was wondering if someone could have a look at my calculations. I believe I'm on the right track but I keep getting wrong answers, but I might be mixing + and - somewhere. I'm also a little unsure about the right way to incorporate the force working on top of the beam.

    The task reads: A combined beam ABCD is resting on a hinged support in A, and on rollers in B and D. In C there is a frictionless joint. There is an evenly distributed load q on top of the beam. Calculate Ay, B and D.

    3. The attempt at a solution
    Due to the number of unknowns I split the beam in C and looked at the two halves independently.

    I've attached my calculations as a file to this post. I'd appreciate it if someone could take a look.

    Attached Files:

    • beam.jpg
      File size:
      18.8 KB
  2. jcsd
  3. Feb 12, 2013 #2


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    Your approach is very good but you are making the same error I pointed out earlier when calculating the distance from the cg of the load to the point A.....you have an extra term in there , can you find it?
  4. Feb 13, 2013 #3
    Yes I got a little impatient there. I tried to delete my first post and use this one instead since it was basically the same question, but no go there.

    Anyway. Looking at Beam ABC from my drawing. If you are supposed to use the length from cg of the load to A, would this be correct:

    q*4,3(the entire length of beam q is working on)*3,35(the length from cg of the load to A)?
  5. Feb 13, 2013 #4


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    Yes, that is correct. The resultant of the distributed load, q*4,3, acts at the cg of the distributed load, 2,15 m from C, which is thus located 3,35 m from A.
  6. Feb 13, 2013 #5
    Thank you.
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