How much eccentricity for a buckling load?

[feajob]

Hi,

As you know, there are a number of semi-empirical formulas for buckling in columns in the intermediate length range. One of these is the J.B. Johnson Formula. I would like to know how much eccentricity (e) you consider for a column with length L?

I am looking for a realistic e/L ratio (rule of thumb which is not too much conservative).

FYI, I found in different stress reports ratios from 1/400 to 1/100.

Thanks,
A.A.Y.

 

[SWComposites]

Well, it depends...
what is the specific application?
how is the load introduced at the ends?
what are the boundary conditions?
how is the part fabricated?

I have seen analysis done with no eccentricity (offset) all the way up to applying a momeent equal to 10% of P.

 

[feajob]

Hi SWComposites,

I am sorry, I did not give you enough details. Following are my responses:

what is the specific application? Landing Gear Structures

how is the load introduced at the ends? A uniform column is subjected to a concentrated axial load.

what are the boundary conditions? Pinned Ends

how is the part fabricated? Machined Parts

Thanks,
A.A.Y.

 

[SWComposites]

Well in that case, the landing gear analyses that I have seen have applied a moment equal to 10% P to account for misalignment and eccentricity, and analyzed the part as a beam column.

 

[feajob]

Thank you SWComposites, for our application it seems to be a reasonable approach.

A.A.Y.