Electrical installation inside RC column

[hoshang]

Hi
Please find the attached images

My friend asked for an advice for this project. I noticed that electrical installation is made inside the RC column. I zoomed in and noticed that the column ties are cut due to this installation. My first thought is to use column jacketting to solve this. The RC columns are carrying two story building. Any other opinions would be appreciated.

 

[r13]

Where is this project located. Any concerns of earthquake, or abnormal high wind? This column is quite sturdy for a two story residential/office building, and may see gravity load only (noting the masonry walls around). Do a quick calculation to see if smaller column fits.

 

[JAE]

If that vertical slot cut all the column ties I’d be concerned no matter what the load.

 

[KootK]

1) I believe that column jacketting would be an appropriate solution and may well be the only way to bring the column into something resembling full code compliance.

2) In a "what do I think will really happen" sense of things, I suspect that the only detrimental impact here is that you probably can't count on the vertical, non-corner bars located on the affected column face when those bars would be compression loaded.

3) Depending on how brave you feel and how tight regulation is, #2 might suggest an alternate solution solution: see if the column would work without the benefit of the vertical, non-corner bars located on the affected column face.

4) I'd be temped to shore the supported beam and demolish and replace the column.

 

[r13]

Usually I'll specify minimum shear reinforcement for case that it's not required. But for your case, I'll,

1. Evaluate shear demand.
2. Compare to code requirement.
3. Determine method of remediation.

Below are requirements from ACI318-08:
Shear reinforcement, Av:
§ If Vu - Φvc > vn,max shear is excessive, revise the section or increase the concrete strength
§ If Vu < 0.5Φvc no shear reinforcement is required
§ If 0.5ΦVc < Vu < ΦVc Av = Avmin ,
§ If Vu > ΦVc Av = (Vu-φVc)*s/φfy*d ≥ Avmin

 

[hoshang]

Hi all
Thanks.
For jacketting, I think I'd suggest four longitudinal angles on four corners of the column and transverse plates on spacings equal to tie spacing of the column.

 

[hokie66]

retired13,
The ties in the column are not shear reinforcement. They are for restraint of the column verticals.

 

[r13]

hokie66,

Yes, if not required for shear and flexural. As the time of cutting, the concrete has hardened. I guess unless the column subsequently subjects to heavy loadings, the confinement/restraint is effective to an extent albeit not fully.

 

[JAE]

If you look at the photos, the cut ties are on the column sides aligned with the beam above. So any shear reinforcement required would not be affected by this cut as the side portion of the uncut ties would be serving as shear reinforcement, if indeed any is really required.

Per hokie66, the concern here would be the loss of constraint of the column vertical bars, which are absolutely required by ACI in all columns.
Without a core cage of reinforcement, this column possibly has lost a significant amount of axial capacity.

 

[r13]

hoshang,

It sounds a way to do it. Don't damage the corners in the process, otherwise, you are getting into bigger trouble than you are facing now.

 

[JAE]

Why worry about the corners?
To get the angles in there it would be perfectly fine to use a chipping hammer to knock away (chamfer) the corners to allow the angles to nest with full contact on the column faces. We specify 3/4" chamfers all the time on columns and concrete in general.

 

[KootK]

For jacketting, I think I'd suggest four longitudinal angles on four corners of the column and transverse plates on spacings equal to tie spacing of the column.

I question the transverse plate idea. Whatever you use for the transverse members, I'd want them to:

a) be in actual, robust contact with the column face and;

b) have enough stiffness that they could convincingly be thought to restrain the compression buckling of the non-corner column bars on the affected face.

Angles might work as the transverse members if you dry-pack grouted the space between those angles and the column or something along those lines.

Keep in mind that you'll probably have to fire proof all of this stuff.

What is you situation with regard to seismic demand and the need for confinement etc?

Can you post a sketch or otherwise describe the disposition of the column vertical reinforcing and ties?

 

[r13]

Damaged corners expose vertical bars. Very difficult to restore the lost concrete required to protect the main reinforcement.

 

[JAE]

A 3/4" chamfer won't expose the corner bars.

But you suggest a good point that with a steel jacket system of some kind there might be a need for fire protection over that steel.
That depends on the building size, and code analysis to determine what level of steel protection is required.

 

[hoshang]

Hi
Thanks all.
For fire protection I'd suggest using gypsum board to cover the jacketting.
Do you agree with minimum of these for the spacing of the transverse plate:
1-16 main bar diameter
2- 48 tie bar diameter
3- smaller dimension of the column
Should the transverse plate be 10mm thick (as the tie diameter is 10mm)?

 

[hoshang]

Hi
Are there any thoughts?

 

[JAE]

hoshang,
Another method of "jacketing" columns.....
A parking garage I was involved in some years ago had been built in the late 1960's.
During the rushed construction (trying to get it built before a World's Fair) the contractor left out some column ties at the bottom of each column where the splices occurred.
After discovery of the issue, they created a series of steel bands around the columns at their bases.
These were comprised of 3/8" thick x 3" steel plates that were fabricated to match the column geometry perfectly...but with some reduced size.
The bands were in two parts, with each half wrapping around each side of the column and meeting at mid-face each side with a turned out tab and a bolt.
The bands were first heated up to expand, then placed on the column and bolted.
As they cooled they tightened around the column in a snug condition.

The theory, I was told, was that they were providing external restraint for the vertical bars, in essence replacing the missing stirrups.

 

[KootK]

Are there any thoughts?

What is you situation with regard to seismic demand and the need for confinement etc?

Can you post a sketch or otherwise describe the disposition of the column vertical reinforcing and ties?

Give a little, get a little.