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Beam deflection

  1. Jul 5, 2016 #1
  2. jcsd
  3. Jul 5, 2016 #2

    SteamKing

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    For the right triangle, the centroid is located 1/3 the base from the right angle or 2/3 the base from the acute angle.

    For the second degree curve, the centroid is also shown correctly.

    You can look these things up to check yourself:

    https://en.wikipedia.org/wiki/List_of_centroids

    http://www.engineering.com/Library/...articleId/109/Centroids-of-Common-Shapes.aspx
     
  4. Jul 5, 2016 #3
    but , the problem is (area AB) x B , so the location should be measured from B , am i right ?
     
  5. Jul 5, 2016 #4

    SteamKing

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    Beats me. The locations of the centroids shown are correct.
     
  6. Jul 5, 2016 #5
    then , what is the purpose of having (areaAB) XA and (areaAB) X B ???
     
  7. Jul 5, 2016 #6
    then , what is the purpose of having (areaAB) XA and (areaAB) X B ???
     
  8. Jul 5, 2016 #7

    SteamKing

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  9. Jul 5, 2016 #8
  10. Jul 5, 2016 #9

    SteamKing

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    Because beam deflections can be calculated using different methods, and he is trying to show the area-moment method in particular.
     
  11. Jul 5, 2016 #10
    i dont understand what is the purpose of having (areaAB) XA and (areaAB) X B ....
    does he mean measure centroid from A and B??
     
  12. Jul 5, 2016 #11
    does he mean measure centroid from A and B??
    why he need to do do?
     
  13. Jul 8, 2016 #12
    why is it so?
     
  14. Jul 8, 2016 #13
    how do you know? can you explain further?
     
  15. Jul 8, 2016 #14

    SteamKing

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  16. Jul 8, 2016 #15
    ok, for Parabolic spandrel , the centroid is 3a/4 , so it's 3(3)/4, but, it'should be measured from B, am i right?
    So is it 1 +9/4 = 13/4 ????
     
  17. Jul 8, 2016 #16

    SteamKing

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    If you want to measure it from B, sure.

    But the location as shown in the OP is also correct, since the spandrel starts 1 m away from B.
     
  18. Jul 8, 2016 #17
    so,
    sorry, it's my fault, then for the smaller triangle part , it should be -0.5(2)(1000)( (4/3) +2 ) , is it true?
    Why the author left out +2 ???
    (area AB) x B means area x distance of centroid measured from B,am i right?
     
  19. Jul 8, 2016 #18

    SteamKing

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    For the smaller triangle, the centroid location measured from A is correct, but the location measured from B is off by 2 m. The 4/3 m should actually be measured from the tip of this triangle.
     
  20. Jul 8, 2016 #19
    so, 4/3 is incorrect?
    the author used (area AB) x B, which means the centroid should be measured from B, right?
     
  21. Jul 9, 2016 #20
    I m not sure what does (area AB x B ) means, can someone clarify?
     
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