12" Dia round opening in (E) Concrete shear wall

[Kadhem]

I'm putting a new 12" dia round opening in an existing special reinforced concrete shear wall. The wall is on the 3rd level parking of 18 level apartment building on top 3 level garage. the coring would cut at least one vertical and horizontal rebar at each face of the wall. any advice about what type of calculations and retrofit are needed and where is the best location to core the hole. my first thought was to avoid the boundary elements, but I'm still not sure how to compensate for the rebars we are going to cut.

Thanks,
AK

 

[Enable]

Definitely don't core the edges of the shear wall and stay somewhere in the field. I cant tell but it looks like you have some openings in the shear wall in the floor above? I'd try to position it underneath those as the load from above is already distributed around that area.

For reinforcement, I may not even worry about a single bar being cut if I could confirm that the reinforcing was per the plans in the area of the core (you'd need to be able to scan to confirm). However, if I was concerned I would epoxy anchor some C-Channels above the opening on either side of the shear wall. Extend the C-Channel maybe 1-2 bar spacings either side (so we don't concentrate the load immediately adjacent to hole). Do so for both directions.

Would need to fireproof the C-Channels. Could be done with intumescent paint or concrete encasement.

 

[HTURKAK]

Will you post the GF and parking level 3 plans ? ..I think the parking levels are basement storey with perimeter walls.

 

[dik]

If you can core at about 1/5 or 1/4 points of the wall it should be OK... assuming the wall is several feet long. You are out of the main flexural field of the wall as well as the main shear field of the wall. A 12" round opening in a wall should not require reinforcement. You might want to use a cover meter to avoid cutting any reinforcing. There are no calculations for this; you can do a FEM study, but it likely wouldn't mean very much... a round hole is the best shape.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Kadhem]

Thank you All for the great comments.

I've uploaded more drawings. Please see attached pdf.

Thanks,
Ali

 

[HTURKAK]

Dear Kadhem (Structural),

I looked to the the dwgs that you have posted.. The lower floors ( parking storeys ) are at basement with perimeter wall and the plan dimensions greater than upper storeys.
-The behavior of framing of basement storeys is outrigger for the upper storeys and GF is transfer plate.
- There are a lot of shear walls in both direction,
- The BM and Shear forces at subject walls will diminish at basement storeys due to outrigger frames and perimeter walls,
- Apparently the critical storey is GF and there are door openings just above the proposed hole at SW 6 . ( the first picture).

IMHO, there is no issue for the proposed 12" dia new holes. I will suggest core drilling ( not chipping ) , and the holes shall be far from the boundary zones and preferably under the door or corridor openings of the GF level.

 

[Aesur]

The way I see if is you have a few options:

1. If you want to replace the reinforcing with an exterior solution, maybe look at FRP as an option. (Force Transfer Around Opening) I highly doubt you will need much force transfer around a 12" opening.
2. Another option would be to check the capacity of the shear wall without those bars, I suspect you will find it still works.
3. Try using the Existing Building Code to show it's less than the allowed increase in utilization/stresses. (probably the easiest)

As others have said, definitely avoid boundary elements or where concentrated loads may be applied above (more reinforcing may be directly below bearing locations).