CONCRETE COLUMN ATOP CONCRETE WALL 3

[sponcyv]

Has anyone ever shown a column coming down on a wall that is thinner than the column. Concrete columns are 14" thick and wall is 12" thick. I don't like this idea. Has anyone ever done this?

 

[JAE]

Doesn't sound like a good idea to me. Usually you see the column footprint extend through the wall (i.e. a pilaster in the wall) to match the column.

I suppose if you check concrete bearing, wall capacity with a concentrated load, and detail the reinforcement to properly lap and tie the two together that it would work. But it would look weird.

My mentors always told me that if a portion of my structure looked weird, then there's probably something wrong with it.

 

[JedClampett]

Forever and ever, when people walk by it, they're going to say, "What idiot decided that a 14 inch column bearing on a 12 inch wall was a good idea?"
Unless you want to answer that or worse, have someone else answer it (maybe agreeing with the questioner), don't do it.

 

[sponcyv]

I agree with you guys!

 

[a2mfk]

JAE- thats classic!
My mentors always told me that if a portion of my structure looked weird, then there's probably something wrong with it.

We'll hopefully see it in a few years in one of those random email forwards of poor construction...

But to be analytical about it, if 2" of the column is unsupported, is it really doing anything? I guess you could analyze it as a tapered column, 12" at the base... But its not the stress at the base that controls the column size anyway, its buckling at the middle?

 

[sponcyv]

a2mfk,

What I failed to mention is that there will be a floor slab at the column / wall interface. That being said, the appearance probably wouldn't be as bad since it is hidden by the floor slab.

 

[BAretired]

With a slab between wall and column, the difference in width will not be seen, so the two inch difference should not matter provided all members are adequate structurally.

BA

 

[a2mfk]

Agree with BA, though I think you are putting a little bit of moment in your column to to the eccentricity, very little though...

 

[ishvaaag]

I have practiced it in cases where a floor is in-between. No problem has resulted in any case. Sometimes I have calculated the thing as a corbel, and in some more conflictive case or just to the whim of some colleague I have made apparent the corbel beyond the floor. I have as well modeled the thing is 3D FEM in similar way to what posted these days here. Rigidity makes that the compressive struts direct very efficiently the load towards rigid support (typically the unloading was on a perimetral wall), and as long unsupported portion is small, stresses are properly limited and reinforcement stays adequate no problem appears.

 

[hokie66]

Not a problem if the load can get through the floor onto the wall. Another example of a poorly presented original post...not trying to pick on you, sponcyv, just saying...

 

[sponcyv]

hokie66 - poorly presented posts are my specialty

 

[sponcyv]

I say that in a joking manner - I always seem to leave something out...I'm trying to get better

 

[csd72]

cponcyv,

No actually I think they are your speciality!

I wouldnt see a problem with it if the bars could be made to work.

I would suggest that you allow for the 1" eccentricity and distribute this between the members according to stiffness and ensure the reinforcement can take it.

I would also suggest you check the slenderness of the wall for issues and the interface stresses if the wall and slab are a weaker concrete than the column.