Non-slender Columns

[slickdeals]

Folks,
I just want confirmation that minimum eccentricity need not be considered for columns that are not slender and be designed only for the actual moments it sees.

The thing that is confusing is the use of the word "shall" in ACI 10.12.3.2 and conflicting information in the commentary where it seems to suggest the contrary.

I would appreciate a clarification.

 

[Lion06]

You are correct. You don't consider a minimum eccentricity for short columns. The column interaction curve already has a minimum eccentricity built into it. The main reason for a minimum eccentricity to be considered in the ANALYSIS portion of slender column design is because if you don't have any bending (i.e. a purely axial load), then you can't, by definition, have any second order effects (which is what the slender column provisions account for).
If you account for cracking, creep, etc. and do a second order analysis of your column (including P-small delta), then you don't have to use the slender column provisions in ACI (except that you still need to assume a minimum e).

 

[GalileoG]

StructuralEIT,

Since when is minimum eccentricity considered in the analysis? I have always used it in the design stage and checked it against the moment I obtained from the analysis stage. Also, minimum eccentricity is autonomos from P-Delta, or so I thought.

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[Lion06]

You're correct, I was just getting at that you can't neglect the minimum e just because you're doing a second order analysis.

Yes, the minimum e is before you do the second order analysis.

 

[Lion06]

I'm sorry, I misread your post with respect to mine. By analysis, I meant the multiplier to get the moment with slenderness effects per the ACI equations.