Ansys eigen value buckling analysis | ASME Section VIII Div 2 part 5 1

[shiraz883]

HI,

I am doing an eigen value buckling analysis using ansys workbench. The FE model is 166° and not 180° (due to some assumptions).

The prestress is the elastic evaluation with primary loads (pressure and deadweight).

Will the multiplier from the 166° model be equivalent to the 360° model?? The load multiplier from 166° model is less than what I get from the ASME code (5.4.1) which means the structure is safe from buckling.

For 360°, I have to model and mesh again and apply the primary loads, solve again and then do the eigen buckling simulation to verify the load multiplier.

Is there any other way to do it?

Shiraz
Sr. Engineer

 

[TGS4]

It is not best practice to use symmetry when performing a buckling analysis. Symmetry automatically excludes buckling modes that are non-symmetric. How have you accounted for that?

Furthermore, I do not recommend using the current (2021) rules for buckling, as they tend to be non-conservative. Please contact me off-line for a copy of the to-be-published 2023 Edition rules. In you specific case, do you actually have a simple geometry and loading that falls into one of the Capacity Reduction Factors in 5.4.1.3? If you have to go with some form of symmetry, my guess is no.

 

[Drej]

You should consider that an eigenvalue buckling analysis will produce primary buckling modes which are optimistic. If the structure has safety critical requirements then you should consider a full non-linear buckling analysis, which is what the code requires you to perform.


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