Column with eccentric load - can it buckle?

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Discussion Overview

The discussion revolves around the behavior of columns subjected to eccentric loads, specifically addressing whether such columns can buckle or if they will only bend. The context includes various applications such as vertical pressure vessel legs, table legs, and posts of a double column car lift.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions whether columns can buckle under eccentric loads or if they will merely bend, highlighting specific cases such as pressure vessel legs and table legs.
  • Another participant notes that eccentrically loaded columns will fail at lower loads compared to symmetrically loaded columns, prompting a need for clarification on the definitions of "buckle" and "bend."
  • A reference is made to the AISC Manual of Steel Construction, which discusses allowable stresses for eccentrically loaded columns, indicating that different failure modes like plastic bending and local buckling are considered, while Euler's theory applies to elastic buckling.
  • It is suggested that buckling implies a loss of stability with significant deformation changes, whereas bending is associated with smaller changes in deformation for small load variations.

Areas of Agreement / Disagreement

Participants express differing views on the definitions of buckling and bending, and whether eccentric loading leads to buckling or bending. The discussion remains unresolved regarding the implications of eccentric loads on column stability.

Contextual Notes

There are limitations in the definitions of "buckle" and "bend," and the discussion does not resolve the mathematical aspects of calculating critical loads for eccentrically loaded columns.

FEAnalyst
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TL;DR
Can column with eccentric load buckle or not?
Hi,

this question is rather simple but it makes me confused after several discussions with friends. Can columns supporting some structure and placed on its edges buckle due to weight of the structure ? Here are the particular cases I'm talking about:
1) vertical pressure vessel's legs
2) vertical legs of a simple table
3) double column car lift's posts

In all these cases load is acting with significant eccentricity/offset. So can these columns buckle or maybe it's not possible and they will only bend ?

If it can buckle, then is it possible to calculate critical load for such case (since Euler's theory assumes load acting exactly in the middle of the column)?
 
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FEAnalyst said:
... columns buckle or maybe it's not possible and they will only bend ...
An eccentrically loaded column will fail at a lower load than a symmetrically loaded column.
You need to define the two terms you use; “buckle” and “bend”.
 
My (ancient) copy of the AISC Manual of Steel Construction, 7th Edition, has a section on allowable stresses for columns with eccentric loading. The book discusses plastic bending and local buckling, while Euler only applies to elastic buckling of the entire column. I would expect that the current 15th Edition would have more information.
 
Buckling is usually understood to mean loss of stability, so that a small change in load causes a major change in deformation. Bending usually means only small changes in deformation are associated with small load changes.
 

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