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new beam to existing column

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gggaa

Civil/Environmental
Nov 27, 2010
3
i'm currentls working on a project where we need to put a new beam to connect to an existing column. what are the ways to place a new RC beam to an existing RC column?
 
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Does it have to be a RC beam? Can you use a steel section? If you can use a steel section the connection becomes easy. If you must use a RC beam, try using epoxy for the bars into the column. Make sure the embedment is long enough to develop Fu of the bars and use shear friction to get the load into the column. I would also shot blast the column face where the beam will attach to roughen the surface to get a higher coefficient of friction.
 
unfortunately, yes, it has to be a RC beam. what if the column is too narrow to develop the Fu of the bars by using epoxy? is there any other way to connect the beam to the column?
 
Is it to one side or two opposite sides?
 
What are the column dimensions? What are your beam dimensions and what forces do you need to dump into the column?
 
Lot of unknowns here. Why can you not use steel or a steel
bracket? Is it a fire rating issue?
 
You could use a steel bracket to make a simple support. But you need to check the column for bending due to the eccentricity (V*e).
 
#6 rebar with hilti adhesive only need 6" emb to develop tensile strength for 4000 psi concret. 4" emb to develop yield.

 
Depending on the size of the column, edge distances might be a killer. There are a lot of unknowns as mentioned before.

If the column is fairly small, it might be better to drill through completely and run continuous rebar and fill with epoxy. That way, there are no concrete failure modes to worry about. Shot blast the surface as SEIT suggested.

 
gggaa,

Are you out there somewhere in cyberspace?
 
When I have this problem, I just look for a place to put another column. If the existing column was intended to support another concrete beam, it should have had provisions for the connection.
 
You could look at removing all the column concrete for the depth of the beam, tieing in the beam rebar and pouring back as part of the beam. Precast columns can be done by this method.

Any load on the column will have to be temporarily resupported.
 
here's a sketch of the beam's location and the dimensions. i apologize if the sketch isn't much help, since i'm new at this.

right now i'm leaning towards making a new column to support the beam, since i don't know if the existing column was designed to carry the load of the new beam.

 
I think that gggaa must be lost in cyberspace.
 
6" x 16" is a pretty slender column. If you can add a new column and support it at foundation level, that would likely be the best solution.

BA
 
Assuming this is only a single storey addition, just adding another 6" to the existing column should do the job, provided the footing is capable of carrying the load. Provide enough drilled in anchorage to tie the two parts together.
 
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