Biaxial Bending plus Torsion

[slickdeals]

Folks:
I have to check the design on a cantilevered stub column with biaxial bending and torsion.

This WF column is a corner column on a parking garage supporting barrier cables. The barrier cables are in orthogonal directions. The forces in the barrier cable is causing a biaxial bending and the eccentricity of the cables is producing a torsion (which is counteracting) and hopefully can be minimized by specifying a stressing sequence.

I want to know what approach I should take to check this column. Obviously there are no axial forces on this column. I have never done a biaxial bending + torsion check on an wide flange beam/column. Any references or suggestions is appreciated.

 

[DHKpeWI]

AISC Design Guide #9 is an excellent resource for torsion and it can be down loaded from the AISC web site. Torsion in open shapes will cause warping which results in stresses that are additive to the bending stresses.

 

[Stillerz]

Pretty sure that any combined stress situations as you described can be check using Chap H in AISC 13.

 

[DHKpeWI]

See also chapter 8 of Salmon Johnson's "Steel Structures."

 

[slickdeals]

I am trying to make sense of H3.3 which is the only place where the code seems to talk about combined bending + torsion on non-HSS shapes.

 

[cntw1953]

Follow Ch-H (Combined Stresses) of AISC ASD for bendings.
I would resolve the net torsion into shear in the flanges.
Depending on the method/detail of connection, the thickness of web could be one thing you need to check on too.

 

[JoshPlumSE]

My advice is this:

1) Get a good torsion reference (either the AISC design Guide or the Salmon and Johnson steel book).

2) Follow the methods mentioned in the torsion reference and don't for a second believe that there is anything in Chapter H that will help you for torsion of wide flanges (or any sections that are subject to signifcant warping).

3) Do a quick hand calculation using the "equivalent tee" method of analysis. This essentially converts the torsional warping stresses from a wide flange into weak axis bending stresses on an equivalent tee. This will give you a feel for how significant (or insignificant torsional stresses really are for your member).

 

[Stillerz]

H3.3 has me a little confused as well.

 

[DHKpeWI]

I agree with JoshPlum. The Solmon Johnson book provides good examples to follow.