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  • Bolt load calculation

    Discussion in 'Calculations' started by moneytree1964, Feb 15, 2013.

    1. moneytree1964

      moneytree1964 New Member

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      Hi Folks.

      I have a calc which I have carried out on FEA but I need to check by hand.

      I have a block which is bolted down using 4 bolts in a line (see below)[​IMG]

      A load 2174 N is applied to the corner as shown.

      What is the load on each bolt ?

      Thanks
       
    2.  
    3. D. Naukam

      D. Naukam Member

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      The load will vary for each bolt. To solve bolting groups in general:
      1) Find the bolt group centroid
      2) Determine directional vectors for each bolt with distance Rn
      3) Calculate direct shear load for both the weight and applied load (Fv)
      4) Calculate Reaction Moment (M) at the bolt group centroid.
      5) Calculate torsional shear force (Fm)
      6) vector addition of direct and torsional shear for total shear load

      Fv = F/A ; Fm = M*Rn/(Ra^2+Rb^2+Rc^2....)

      Ra=distance from group centroid to bolt A
      Rb=distance from group centroid to bolt B
      Rc=follow the pattern....

      Torsional shear will vary for the inner bolts and outer bolts. The further from the bolt group centroid, the less this will be in the diagram you have supplied. Fortunately, all bolts are in a single line making reaction vectors easy to calculate. The vector addition of the torsion and direct shear vectors will result in a different shear stress for each bolt.

      As an aside, when doing FEA, it is important to understand the fundamentals. Do a few trials on a simply beam until you trust the software. When you get an answer, you should be able to observe the outputs and determine if the answer generated by the software was acceptable. Stopping and questioning the output once in a while is a good thing. As we have here, comparing the output to hand calculations is very nice to see.
       
    4. mvalenti

      mvalenti Well-Known Member

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      yes, what he said...
       
    5. shyamdikshit

      shyamdikshit Member

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      [h=1]D. Naukam has correctly explained in detail. Consideration is all bolts are of same size.[/h]
       
    6. moneytree1964

      moneytree1964 New Member

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    7. PierArg

      PierArg Well-Known Member

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      Thanks for sharing this site!
      I found it very interesting and I have already saved it in my favourite sites.
       
    8. svenny

      svenny Member

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      Not sure of your application, but something like that should have two dowels so that Bolts aren't being used to support the torsion force.
       
    9. beerion

      beerion New Member

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