COLUMN SIZE INCREASE
COLUMN SIZE INCREASE
(OP)
Hi,
RC column of size 18"x18" column height 11' have to be increased to size 30"x30"
how can we do this? building is under construction just columns are constructed upto 11' height on a raft 24" , design revision says column should be increased. code followed UBC 97, seismic zone 3. two more stories will be raised on these columns.
Regards
RC column of size 18"x18" column height 11' have to be increased to size 30"x30"
how can we do this? building is under construction just columns are constructed upto 11' height on a raft 24" , design revision says column should be increased. code followed UBC 97, seismic zone 3. two more stories will be raised on these columns.
Regards






RE: COLUMN SIZE INCREASE
I assume that you have two way concrete floor slabs/no beams at columns. Have they cast the first slab over the column(s) in question yet?
RE: COLUMN SIZE INCREASE
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: COLUMN SIZE INCREASE
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RE: COLUMN SIZE INCREASE
@view in plan,building is irregular triangular with 50' span in center and than decreasing on both sides ending with base of 24' x 111' rectangle. I couldn't upload here, i d try uploading plan later. columns supporting beams 24 x 36 and beam column capacity ration exceeds so to increase the column sections. any idea about making old and new concrete behave together.
thanks all
RE: COLUMN SIZE INCREASE
Often you can even consider the existing bars for shear transfer, if your finished column can be considered pin-pin.
Note that on the three occasions I've detailed this, only one was built. Once the builder sees the level of work, it is more likely that JAE's solution is going to be selected.
RE: COLUMN SIZE INCREASE
This all tips the scale further in favour of demolition.
The new ring of concrete that you're considering casting will likely be doing the bulk of the column's work when it's all said and done, particularly when it comes to satisfying the intent of the column/beam ratio. Perhaps the inner core of existing concrete could be ignored altogether.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: COLUMN SIZE INCREASE
If the beam & slab supported by this column have not yet been cast, I would recommend demolishing the smaller column and constructing the proper size column. The preparation necessary to "wrap" the existing column, combined with the cost of additional rebar & formwork, combined with the time needed to accomplish all of this, will undoubtedly be more than removing the smaller column. Just be sure to preserve the existing raft-to-column dowels in the process. You will no doubt need to increase the size/number of dowels coming out of the raft.
Ralph
Structures Consulting
Northeast USA
RE: COLUMN SIZE INCREASE
RE: COLUMN SIZE INCREASE
If you are using vinyl epoxy, you will need to ensure you provide fire protection (and no, just encasing in concrete at typical clear cover does not suffice from what I've heard).
Think about it: If you place your bar correctly at the corner, the epoxy extends out from this and can melt/break down during a fire. Some do have reasonable fire tolerance, but check the product carefully - Better yet, call the manufacturer for support.
RE: COLUMN SIZE INCREASE
RE: COLUMN SIZE INCREASE
RE: COLUMN SIZE INCREASE
RE: COLUMN SIZE INCREASE
RE: COLUMN SIZE INCREASE
RE: COLUMN SIZE INCREASE
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: COLUMN SIZE INCREASE
RE: COLUMN SIZE INCREASE
RE: COLUMN SIZE INCREASE
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: COLUMN SIZE INCREASE
actually they have also cast a reinforced basement wall all around the columns periphery when design was revised it was failing in beam capacity ratio I suggested increasing column sizes but contractor have to do lot of chipping and drilling, and anchoring chemical so the need more options. i have all span varying like structure is a triangular in about both sides of the central span. central span is 49' than on both sides spans are 41' than 35',27'.columns on central span are 24x24 with 24x36 beams,41' span has columns 24x24 with 24x36 beams than comes 35'span it has 18x24 beams, 27' span also have 18x24 beams.
RE: COLUMN SIZE INCREASE
WiQi, You might get better suggestions if you were to post at least a plan showing the structure around the column of concern.
Ralph
Structures Consulting
Northeast USA
RE: COLUMN SIZE INCREASE
RE: COLUMN SIZE INCREASE
RE: COLUMN SIZE INCREASE
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: COLUMN SIZE INCREASE