Composite columns

[joemarch]

I have a situation where I have 10x10 tube columns. The architect wants to encase them in a 16x16 concrete to protect them and give them the "parking garage look". I'm not relying on the concrete to provide any structural value. I'm still plan on puting a #4 in each corner and having #3 ties. Do I have sufficient cover? Will there be any problems with doing this?

Thanks

 

[SperlingPE]

Is there any bending on the column or only vertical load?
Will you be filling the 10x10 tubes or just encasing?

 

[joemarch]

The 10x10's will only see vertical loads. I'm only going to encase the 10x10's. I also have a few wide flanges that I'm going to encase that do see bending.

 

[TPNY]

Since you titled the thread "composite columns" I'm assuming that the tube steel is encasing a concrete core. I can just imagine a car bumping into the columns and chunks of concrete falling off at the corners where there is only 1.5" cover (3" thick concrete - #4 lat. bar dia - #3 tie bar dia - .5" concrete between tube steel and reinforcement)... That is, if this is actually a parking garage...

Couldn't the parking garage concrete look be more reasonably obtained with a mesh and thin stucco coating, or something similar? Architects... *sigh*

 

[TPNY]

Opps, I guessed incorrectly about the steel encasing the concrete. I guess this should be more appropriately titled "columns that are mucked up by archtects."

(I'm not really a bitter person)

As a side question, why not have the columns be made solely out of reinforced concrete?

 

[joemarch]

Zo40, Well I think the architect wants something a little more durable than a wire mesh with a stucco coating. I guess thats why I pursued encasing them with concrete. I was just wondering how durable the concrete would really be? I was thinking it fairly durable with ties at 12"o.c.

 

[joemarch]

Zo40, All my other framing is steel. Plus I have some wind frames and sort. Not all my columns need to be encase. I thought I would just keep it simple.

 

[TPNY]

Fair enough. I guess if it's only for a couple of columns, then the cost difference won't matter as much. But have you considered constructability? You will have to make forms and tie rebar anyways (as you would if you were to make the entire column of concrete), not to mention getting the concrete to fill up that 10' long 3" space with rebar, without getting too many voids.

Is there a tile or panel out there that will give you the look and durrability of concrete that you can just affix and seal-up the seams?

 

[SacreBleu]

Can you convince the Archie to use sonotube-formed, circular concrete encasing the 10x10 steel?

 

[SperlingPE]

I have seen this used in the office I work at to protect steel columns. The concrete only went up about 8' on the column. This was in a warehouse. Minimum vertical reinforcing was specified and ties were provided.
Questions I have:
1. Is the clumn painted or black?
2. Do you provide a bond breaker between column & concrete?
3. Sonotube forms leave the tell tale marks, what do you do about that? Is there a inexpensive circular form that does not?

 

[joemarch]

Convince an architect?? You have to be out of your mind! He is set in his way. Frank Lloyd Wright must have not have used circular columns before!

 

[JAE]

joemarch,
I've seen many steel columns encased in concrete for fire protection requirements in parking garages. If this is in a situation where there will be lots of outside air-moisture, or where moisture may be dropping down from above, what usually happens is that the moisture gets in between the steel and concrete and initiates some surface rusting - with the resulting expansion, you end up with longitudinal cracks in the encasement and eventually chunks falling off.

Most of the "bad" conditions I've seen have no reiforcement at all so by adding some nominal rebar and ties you will probably keep the concrete fairly intact. If you are not in a moisture prone environment I wouldn't worry about it as long as you do reinforce it as you've stated.

Just remaining is the issue of cost which other members have implied above.

 

[SacreBleu]

Sperling and joemarch:
To me, "parking lot columns" are frequently circular. I can not see how sonotube "marks" can ruin anyone's day. In fact, there is an underground parking area where the maintenance crew wrapped the columns in carpet, since it is a tight squeeze for parking.

 

[joemarch]

Thanks everyone! You all were helpful.

 

[jheidt2543]

If the sonotube marks are really that much of problem, you could call for the columns to have a rubbed finish. Nothing like adding lots of dollars to a project. Do you think the cars care if the columns are rubbed or not?