Repair of shear damaged columns

[rhinoconsulting]

Hey everyone.
My boss has been given a job to inspect a damaged column in the basement of a high rise building.

The column is picking up podium slab loads but not taking significant axial forces.

The column has a large diagonal crack spanning side to side in the long direction and completly through the column. The crack is much wider in the middle around 3mm and tapers of towards the edges.

His thoughts are the post tensioned slab over stressed the column around its strong axis leading to shear failure.

Has any one dealt with a similar problem ? is there any good documentation for dealing with these problems ?

Cheers

 

[msquared48]

The diagonal cracking implies shear, but where is the crack vertically on the column?

Supporting the podium slab, is there another column above this one?

Did the crack appear before or after the post-tensioning?

If it is not taking substantial axial forces, could it be in tension?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[JAE]

You might consider wrapping the column in steel bands.

This is done by using perhaps 3/8" x 3" (sorry about the inches) steel straps as pseudo stirrups. You can detail them to be just short of the column widths. Have the welder heat the tie straps to expand them - weld them off - and as they cool they contract around the column.

I would also suggest epoxy injection in the cracks.

All this is predicated on you knowing exactly what happened, why the crack occurred, and probably doing a load analysis so that you very clearly "understand" the column and its behavior.

 

[hokie66]

Based on your description, I agree with your boss as to the most likely cause, provided the column is near the edge of the stressed floor. Any chance of a photo?

 

[hokie66]

Another reason for columns to crack as described is that they are too short. When they are very short and therefore very stiff, shrinkage of the slab will break them. I have seen this where a column projects from the top of a wall.

 

[rhinoconsulting]

Thnaks for the responses.

I don't have drawings or photos yet But ill bump the thread when I do.

msquared48

I doubt the column is in tension there is no tension cracking.

Also there is no direct column above it.

hokie66

Although I have no seen the detail its a basement carpark. So it would not be too high. I think his pretty confident it was overstressed during in construction but its hard to tell how long the crack has been there because there is no documentation of it previously.

JAE

Once we get some drawings we can do some analysis. Just wanted to get some ideas.

 

[tai99]

Could it be buckling? For such case, there should have indication of concrete crashing.