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Kl/r Ratio of The Steel Column ????

Kl/r Ratio of The Steel Column ????

Kl/r Ratio of The Steel Column ????

(OP)
I am designing a steel shed in SAP2000 (Sizes 29.5mx43.2mx9m) shed have 2 span so intermediate column length is 10 m and for this column Sap is giving me warning that the column Kl/r is increasing by 200 (actual ratio coming 256) so my question is that can I ignore this warning if not then how I can fix this problem any economical solution however stress ratio of this column is 75% so I don’t want to increase the column section any other reasonable solution regarding this.
Waiting for your valuable reply thanks in advance

RE: Kl/r Ratio of The Steel Column ????

I'd increase the size of the column. The economic impact will be minor. And your 75% may not be a great representation of the capacity of your slender column that will be rather sensitive to accidental eccentricities and imperfections. Other options might include fixing the top and/or bottom of the columns to reduce the effective length. You could also brace the column part way down with braces back to the roof (tree column-ish). I'd expect all of thes option s to be more expensive than just increasing the column size however.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Kl/r Ratio of The Steel Column ????

(OP)
I tried to solve this problem by changing the section as you suggested above, I tried the section
UB 610x229x140 still the warning appears and before I was using the section UB457x191x67 this much different does not solve my problem, still if I go with this option my boss will kill me wink
I cannot provide bracing because of the block wall between the steel columns, by using the block wall I can reduce unbraced length of the column by providing some connection through angels or plates????

RE: Kl/r Ratio of The Steel Column ????

Try UC sections.

Cheers! -VH

RE: Kl/r Ratio of The Steel Column ????

Connection to the wall may indeed work. But so should selecting a suitable column. As suggested above, a designated column section may be the way to go. I'd check kL/r by hand before selecting a new colun in your software package to ensure that slenderness works.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Kl/r Ratio of The Steel Column ????

Sounds like a hollow steel column would be the way to go. HSS 152 x 152 x 4.8 weighs only 21.7 kg/m and satisfies the L/r requirement.

BA

RE: Kl/r Ratio of The Steel Column ????

"so my question is that can I ignore this warning"

Ignore it and you can then follow up in the Engineering Failures forum. Why do you think this limit is required?

RE: Kl/r Ratio of The Steel Column ????

there should be kl/r "200" value that you can change to another number. I don't think this is a requirement but "preferable" per AISC.

RE: Kl/r Ratio of The Steel Column ????

I believe when it comes to compression members, there's no leeway. Tension members they have leeway in the 300 number if the attached components can handle the possible additional deformation.

RE: Kl/r Ratio of The Steel Column ????

KL/r can exceed 200. Per AISC Spec Section E2 - 'it isn't preferred' but it does not state that you cannot exceed the 200 limit. I believe the old ASD code did maintain that you CAN NOT exceed 200.

RE: Kl/r Ratio of The Steel Column ????

Well, be that as it may it's no an envelope I'd care to push as buckling occurs suddenly, without warning.

RE: Kl/r Ratio of The Steel Column ????

What's the buckling load factor?

RE: Kl/r Ratio of The Steel Column ????

UB 610x229x140 is the wrong shape to be using because of its low ry value. Use an HSS instead.

Also, if applicable, you may wish to consider the possibility of forklift trucks colliding with the column.

BA

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