
Re: How would you manage buckling calculations without buckling module in Solid Works ?
Keith Frankie May 31, 2016 4:48 PM (in response to Grzegorz Janisz)If I read the SW product matrices correctly you have access to "static" studies only with your "SW Premium" license.
You should be able to activate the "large displacements" flag to invoke the nonlinear solver. You'll be missing most of the features of the "nonlinear" study type, but it should be close enough. You'll be required, unfortunately, to use a solid mesh (which will really slow this down).
For the attached part the first "static" study, titled "static only" solve with a load of 20,000 lbs. The study has been copied over to create the second "static" study called "static large displacement". The "large displacement" option has been turned on under the study properties. Now the study runs at 15,000 lbs but fails at 16,000 lbs. This indicates the buckling load is somewhere between these two points.
Using SW Simulation Professional to confirm this the buckling load is found to be 15,764 lbs.

control static only.SLDPRT.zip 52.7 KB

Re: How would you manage buckling calculations without buckling module in Solid Works ?
Grzegorz Janisz Jun 1, 2016 8:01 AM (in response to Keith Frankie)Hi Keith,
I checked it on a simple post and it failed on 21 kN exactly like equations results
However What If I had landing like the one I attach ? I checked it and it didn't fail even with 85 kN on Landing. I'm not sure but I have a feeling that keeping 85kN it wouldn't be stable. What happened if you analyse it with buckling mode ?
P.S. Yes, I have only static analysis.

main assembly.zip 13.2 MB

Re: How would you manage buckling calculations without buckling module in Solid Works ?
Keith Frankie Jun 1, 2016 11:56 AM (in response to Grzegorz Janisz)Nice simplified test assembly.
A SW buckling study says that with a 10 kN vertical load failure will occur at a load factor of 22. That scales the sideways force too. I got the 'large displacement' study to run at 160 kN (with solver restart), but not at 180 kN. I noticed one of the C channels on top is twisting a lot. I split that surface and removed the load from the center half of the span. This does make the static 'large displacement' study run for higher loads. I'd assume you're more worried about column buckling than C channel twisting. Of course this leads to unequal column loading, but oh well. The buckling study now says load factor of 24.
With the 85 kN load I see the posts are only displaced sideways by 25 mm, which doesn't seem like that much compared to the 80 mm post size, and considering top and bottom are fairly fixed against rotation. What do hand calcs show for the strength of a single column under similar loading?
For the static 'large displacement' study the OUT file says 3 iterations at 10 kN load, 7 iterations at 85 kN load.

Re: How would you manage buckling calculations without buckling module in Solid Works ?
Grzegorz Janisz Jun 2, 2016 7:42 AM (in response to Keith Frankie)Hi,
It's just a test model, normally I would rather make frame analysis, it's not in real life . I just wanted to find out how does it work if I have only static module.
For single post, force is 21 kN and this is exactly how model fails with large displacement analysis. Btw in buckling analysis we care only about vertical force, don't we ? If there appears moment like in this case, then standard static analysis is involved?
Thanks a lot for help ... Now I know who schould I turn to when it's about buckling

Re: How would you manage buckling calculations without buckling module in Solid Works ?
Keith Frankie Jun 2, 2016 12:57 PM (in response to Grzegorz Janisz)For a single post, with I = 2.2 in^4, L = 185in, and E = 30.5 x 10^6 I see a clampedguided buckling load of 86 kN per Columns: Critical Load
86 x 4 = 225, which is about the strength SW buckling study got for your assembly (10kn x 22 load factor).
Buckling failure need a little sideways 'kick' to get it going. A perfect structure in CAD will just compress, which isn't realistic. Real world conditions provide this. In CAD either a small sideways force or a geometry or loading asymmetry do the trick. I'm not clear on how much is needed.



