Reconnecting new flat slab to existing column

[ajk1]

I am looking at several options to deal with a badly deteriorated 2-way flat slab in an underground parking garage below a multi-storey superstructure. One option is to demolish the floor slab and rebuild it, but I am not sure the best way the connect the new floor slab to the existing reinforced concrete supporting columns.

Anyone have any suggestions on how to connect the new floor slab to the existing square spirally reinforced concrete column?

The columns are sitting on caissons, so I could enlarge the column and take it down thru the s.o.g. to the caisson, but that would narrow the parking spaces.

Another idea is perhaps to bolt a steel bracket to the sides of the existing column, but although it is a square column it is spirally reinforced so it would be difficult to install bolts.

 

[Canuck67]

Typically, during demolition the structural slab is sawcut approximately 3'-0" away from the column face (and walls). Once the main portion of the slab has been removed (usually via sawcutting and removing slabs), the remaining concrete around the columns and walls is jackhammered. This removes the concrete, but leaves a lap length of the steel. At slab level, the concrete is also jackhammered out to form a chase, typically to the depth of concrete cover for the vertical column (or wall) reinforcement. This provides a bit of a socket as well as the lap length for rebar, or for couplers, etc... If all the rebar is in good condition, then great. If the rebar is deteriorated, then one must look at alternate solutions which include, but are not limited to adding steel angles to jacket the column below slab level, drilling and installing new rebar through column, adding concrete capitals, etc..

All of the above techniques have been completed in the past by the company that I think you work for and of which I used to work for many years ago. There should be some in house expertise and details for this type of project as they have completed many in the past of which I have been part of several.

 

[ajk1]

Yes but I was wondering if there was something more elegant. Drilling thru 30" spirally reinforced column supporting multi-storey tower above does not seem that practical. There is a much more elegant solution that has been used (not by us) but I am not entirely comfortable with it even though I have been assured by an academic that it is ok if done right. I will stick to the more mundane way of doing it.
Are you in Toronto? Just curious.

 

[Canuck67]

I agree that drilling through 30" spirally reinforced columns is not ideal, can be difficult depending on rebar congestion, but is an option. I guess I am always the optimist in hoping that the existing rebar has minimal loss of section, because it makes things much easier. I am interested to hear what the more elegant solution may entail. I typically do not practice rehabilitation much anymore on a large scale as the building stock where I am located is much smaller. I used to work in Toronto, but now am located an hour north of the city.