Hello everyone,
I would like to receive suggestions on how to improve my analysis' reliability when I am designing a floating barge and wish to get results on it's critical buckling load.
On my stress analysis I use springs on the bottom of the barge, simulating the water effect because I cannot add hydrostatic pressure to the bottom. That would be impossible, as the balance of forces would be different of zero, resulting in an analysis failure.
So far it's OK, I'm able to perform stress analyses of floating barges with my "method" perfectly, My results on stress analysis are very reliable.
The problem comes when I try to perform a critical buckling load analysis. When I have all my model supported by springs, I can't get any result; at the end of the analysis I only get a result similar to the result when I perform a "Check Model".
When I add some Nodal General Constrainsts on my model the critical buckling load analysis works fine. The problem is, it becomes unreliable, as my model should be floating and not being supported by anything but water.
Again, any suggestions on how to make my model reliable on critical buckling load analysis?
Thanks
Best Regards,
Yossef Sami El Didi
Solved! Go to Solution.
Solved by AstroJohnPE. Go to Solution.
Hi Yossef,
If the critical buckling analysis is giving no results (which is different than giving results of 0), there should be some type of message in one of the analysis logs. Use the Report tab to view the Log and Summary files.
Also, you might be able to learn something by running a Natural Frequency analysis or Natural Frequency with Load Stiffening analysis. There could be something "strange" occurring with the frequency that the Critical Buckling analysis is having problems with. If any of the frequency results are 0, then your model is not constrained in all directions. Are you using springs to hold it in X, Y, and Z?
On a separate issue, how many springs are you using in your model? More than 3 nodes? To have a statically stable model in all 6 directions (X, Y, Z translation, rotation about X, Y, Z), you only need to pin 3 nodes not in a straight line. So you might be able to apply your hydrostatic pressure like you suggested and use springs in X, Y, Z at 3 (or more) nodes to balance out the hydrostatic pressure. After you get the results, check the forces in the springs to confirm that the load is sufficiently close to 0; that is, the hydrostatic pressure almost balances the gravity load.