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CPEProjE
Posts: 19
Registered: ‎09-09-2013

FEA Results follow up

122 Views, 1 Replies
02-10-2014 09:40 AM

Forum,

 

Please take a look at the following file; it is a 1/4-section of a skid assembly with x- and z-symmetry applied.  I loaded that section with 162500 lbs (6.07 psi see 2nd screen shot for location of water weight/force).

 

My question is, if the total weight over the entire skid area shown is 650,000 lbs, should I have entered that value in the -Y instead of the 165000 lbs?  Does Simulation treat that number as the whole or strictly as the weight/force applied to that quarter section?

 

Secondly, I chose brick elements for both the plate and beams (solid) with mesh settings at 15%.  Are my results skewed with incorrect element type?  After initial mesh, should I have changed the actual W12x96, W8x31 and L3x3x3/8 to beam then made the associative selections in element definitions?

 

I ran the test in 2 ways:

  1. 650,000 lb load in the quarter section; displacement results were 0.0395 w/ Von Mises of 24,668.24 psi
  2. 162,500 lb load in the quarter section; displacement results were 0.011 w/ Von Mises of 6,398 psi

 

 

Regards and thank you for looking.

 

skid floor displacement.png

 

skid floor loading1.jpg

 

skid floor loading2.jpg

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Active Contributor
Stefan2653
Posts: 41
Registered: ‎11-03-2011

Re: FEA Results follow up

02-10-2014 11:15 AM in reply to: CPEProjE

Hi,

You should be good with the 1/4 load on 1/4 of the model.

 

The accuracy of the results depends on how the thickness of the "thin" sections are meshed. At a minimum you should have at least two elements thick in the "thin" sections. Displacements can be reasonably accurate with a lower mesh density, but the stresses could be significantly off if you are only one element thick.

 

The best approach to a satisfactoty mesh would be to perform a convergence study. Plot the peak stresses with your 15% mesh density, then with several tighter mesh densities (e.g. 10%, 7%). When the stress values vary by a few percentage points between mesh density runs (or by a value you deem acceptable based on your overall stress margins), your results should be acceptably accurate.

 

You could also mesh the assembly as plate elements and connect your I-beams to the floor with stiff beam elements.

 

Stefan

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