Correlation between Buckling Theory and ANSYS results

  • Last Post 15 September 2018
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sujaysanjiv posted this 14 September 2018

This should be quick.

I was running a linear buckling analysis on a 25 x 1 x 0.5 inch Fixed-Free Column. The compressive stress distribution was established by subjecting the column to a 1.0 lbf compressive load at the free end and the results transferred into the buckling analysis. The load multiplier output value I obtained was 1196.8 and 4776.7 for Mode 1 and Mode 2 respectively. I did a hand-calculation using the Euler Column Formula for the particular end conditions and obtained a critical load of 4766.787 lbf which closely matches the value for Mode 2. So what is the significance of the mode 1 value? Why does ANSYS return this value? If such a column is ever designed, what load would it buckle at, in the real world ? I am just trying to wrap my head around this correlation.


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peteroznewman posted this 15 September 2018

You can use the Euler formula to calculate the area moment of inertia about two different directions, the thin and the thick direction. If the column is free at the top, then it would always buckle in the thin direction. But if the column was supported at the top in the thin direction only, then it would buckle in the thick direction at the higher load.



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sujaysanjiv posted this 15 September 2018

Thanks Peter!