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Does Angling a pin support on a truss change anything?

  1. Apr 15, 2015 #1
    1. The problem statement, all variables and given/known data
    If you had a simple 2D truss with a pin and a roller support, would making the pin on a 30 degree incline change the supporting reactions?

    2. Relevant equations

    3. The attempt at a solution
    Can't see why since it still supports a horizontal and vertical, don't know hwy the angle would change anything?
  2. jcsd
  3. Apr 15, 2015 #2

    Simon Bridge

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    How did you determine that it does not change anything? Did you draw a diagram and work out the forces and stresses?
    How are is the pin usually angled IRL - did you have a look?
  4. Apr 15, 2015 #3

    Okay so, imagine a basic truss that has a roller on the left side and a pin on the right. The pin on the right it angled at 30 degrees so instead of it sitting under the end perpendicular to the truss, its tilted by 30 degrees. Does tilting the support change the external reactions?
  5. Apr 15, 2015 #4
    See attached

    Attached Files:

  6. Apr 15, 2015 #5


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    It depends.

    Are you more concerned with the reactions in the pin itself, or are you concerned with the forces at the base of the pin holder?
  7. Apr 18, 2015 #6
    Yeah im concerned with just the external reactions of the pin support. Like in that picture I added, would tilting the support 30 degrees underneath the truss create a horizontal reaction? or would it still be 0 because there is no horizontal load?

    PS. there are point loads on the truss at joints but none at the pin support and none are angled or horizontal
  8. Apr 18, 2015 #7


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    As always, if you want to know what is going on in the pin and its foundation, make a free body diagram and analyze it.
  9. Apr 20, 2015 #8
    Can you please demonstrate how to draw the free body diagram start from the 30 degrees angled pin support? Let's say we put an external load 15kN pointing downward at top left corner of the truss. How to find the reaction forces at both roller and pin support? Do we consider the actual 2 reaction forces of the pin support as resultant force and both of them have their own horizontal and vertical forces?
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