FEA Results follow up

[CPEProjE]

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

• Skid quarter section is the link if anyone interested in pulling down and re-evaluating.

Regards and thank you for looking.

[Stefan2653]

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