Biaxial Bending in CHS

[handex]

Just looking for this to be cleared up. In as4100 it has requirements for biaxial bending depending on whether or not the section is compact etc.

For a CHS I would have thought these would not apply, since a resultant can be found from the moment components, and the problem reduced to uniaxial bending. Is this the way most people go about it?

 

[Lion06]

If CHS is Circular Hollow Section, then yes, but I use AISC.

 

[apsix]

I agree, the concept of biaxial bending is meaningless for CHS sections.

 

[a2mfk]

Also may be easier to model it as one resultant force and one moment. Curious though, what type of structure are you designing that has a pipe in bending? Not something you see everyday..

 

[sdz]

You can consider it as unixial bending using the maximum moment about any axis, i.e. the vector sum of x,y moment components, but you will still need to check the effect of the section being non-compact

AS4100 5.2.2 Section slenderness
...For circular hollow sections, the section slenderness shall be calculated as follows: Ls=(do/t)(fy/250)

 

[handex]

yeah I always take into account the effects of it being non-compact. Its for a flagged supersite sign so has bending and torsion due to wind and deadload due to the approx 12m cantilever.

I have always combined moments and get a resultant but a colleage suggested I followed the code, but as you guys have confirmed its really uniaxial bending.

 

[rscassar]

Biaxial bending of a chs should be resolved into a uniaxial moment and designed accordingly. After all, a chs only has 1 axis. What size tube are you using for your 12m cantilever?