Slender Concrete Column Design AS3600

Question

Slender Concrete Column Design AS3600

asixth (Structural)

(OP)

24 Mar 12 03:41

Hi Guys

Does anyone have any tricks for designing slender concrete columns where the Le/r ratio starts getting higher than 50.

I am noticing a large fall away in strength for columns with high Le/r.

Does anyone know how to reduce the effective length factor, I normally use a ke=0.85 for braced columns and sometimes get it down to 0.8 by calculating buckling effective lengths in FE packages. I haven't explored too much into the graphs used in AS3600 for the calculation of effective length factors.

Does anyone have a good justification to not consider the minimum eccentricity provisions of AS3600?

I have attached the 2 column design curves for an 800x300 column for Le/r's of 25 and 60. I have walked passed many columns thru the city which are very slender so I am looking for a way to push my columns skinnier.

Thanks and regards

sdz (Structural) · Answer 1 · 2012-03-29 07:54:24

1. Increase the column dimensions. But that's probably not the answer you're looking for.
2. Can you brace it at mid height? Perhaps a couple of CHS braces would work without being too obvious.

asixth (Structural) · Answer 2 · 2012-03-29 08:02:32

Yeah, they both weren't really the answers that I was hoping for. Good answers, but I was hoping someone had some tips on how I can push my columns right to the limit like justifying that the 0.05*D min moment isn't required.

sdz (Structural) · Answer 3 · 2012-03-29 08:07:37

Why is it so important? Are you trying to keep an architect happy?
Better to sleep well at night.

asixth (Structural) · Answer 4 · 2012-03-30 05:46:31

Yeah, the architect likes skinny columns and so do I.

hokie66 (Structural) · Answer 5 · 2012-03-30 05:56:03

Those slender columns in the city look too skinny to me.

rowingengineer (Structural) · Answer 6 · 2012-03-30 17:56:58

I don't like to push the b'ndy to much. I know some engineers used to consider blade columns as blade walls, but this practice has been stopped with the 2009 code.

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Slender Concrete Column Design AS3600