Column Shear!!

Hello:
This was a question i asked earlier in one of the thread but did not get much replies.My question was in cae of columns subjected to bending moment+axial load, we design these according to our interaction curve(check for Pu and Mu), but we never make any check for shear.Just like in beams it is imperative to check for shear capacity why not in columns .The columns too are subjected to horizontal shear.We provide ties but it may not be that these ties may adequately serve the above purpose.

 

[Kramer]

If the lateral loads are being resisted by elements other than the columns (shear walls, etc.), the shear force in the columns may be low, but should still be checked.

 

But, my question is that are we doing that in professional design practise?
tabz

 

[breaks]

Yes, shear should be checked in columns. The reason you probably don't hear more about shear in column design is that most columns are primarily there to support a certain axial loading, not shear.

Shear loads are normally taken into account for the entire structure or column/beam system. The wind load is usually the primary horizontal/shear load and the entire structural system works in unison to resist this loading. This loading is most often resisted by shear walls or bracing that distributes the horizontal loading to the columns' foundations.

Basically, shear should be examined on a case-by-case basis. Oftentimes this "shear" is resisted by the entire system and not one or two columns.

 

TABZ,

An emphatic "YES" is the answer to your question, shear must be checked and the tie size and spacing should satisfy shear also particularly in earthquake prone areas the story shear is all concentrated in the column bottoms and maust be satisfied.

 

[boo1]

Agree with Breaks. The shear is checked. I treat columns with a design methidology checking each step, which includes shear calcs.

Cheers

 

[rory01]

Let me ask this. For a column that has very little externally applied shear or moment, that is in uniaxial compression say, do we check for the maximum (diagonal) shear stress which we would say is about half the compressive stress?

 

[JAE]

Most columns are in compression (duh) and the phiVc capacity shoots up dramatically. In addition, the cross sections of columns required for axial/buckling tend to have phiVc values far in excess of the shear that is generated by wind....less so with seismic.

Your question centers around what is "typical practice" for engineers. I would suggest that many older engineers checked columns for a while and found that it never came close to controlling as the phiVc was high....so they gradually stopped checking it.

Technically, you MUST check it. With experience, you should be able to get a feel for when it would be a controlling factor.