Jacketing or Strengthening for Existing Columns 1

[MSUK90]

I was checking columns for a ground villa where they have increased the floor height by 1m more than the approved height.
Many columns are failing in buckling now. However, when I change the column thickness from 200mm to 250mm, the columns passed the buckling check.
My question is regarding jacketing at site. Is it possible to just increase the concrete thickness to existing columns(without adding reinforcement)?
Has someone has experience doing such thing?
I would like to get some detailing drawings for this type of work or even drawings for jacketing with additional reinforcement.

 

[Enable]

Found the detail from the EOR

We couldn't do exactly what they wanted as the angles into the column were impossible to facilitate on both ends with a single stirrup. We therefore epoxied the angled stirrups into the column on a single side and welded the laps.

 

[MSUK90]

Found the detail from the EOR

Amazingly, the detail you have shared is pretty much same which I have finally given them based on my understanding. However, the stirrups I have shown in the detail were not bent to 135[sup]o[/sup] as you have shown and just 90[sup]o[/sup] with around 50mm embedment into the existing concrete. I really do hope that doesn't possess much of an issue in the performance.

Also a big thanks to you for remembering and posting the details.

 

[jayrod12]

Only 50mm embedment into the existing concrete? Seems quite low. Wouldn't you want to develop the bar into the existing concrete?

 

[CrabbyT]

How about a carbon fiber wrap?

https://www.youtube.com/watch?v=7bcnHg76uwk&ab_channel=Sika

https://usa.sika.com/en/constructio...-strengthening/fabrics/sikawrap-hex-230c.html

 

[MSUK90]

Wouldn't you want to develop the bar into the existing concrete?

Didn't quite observed if stirrup also require development length.

 

[MSUK90]

How about a carbon fiber wrap?

That also can be considered, but I think it just help in increasing flexural strength of the element. Isn't that so??

 

[CrabbyT]

That also can be considered, but I think it just help in increasing flexural strength of the element. Isn't that so??

No - wrapping a column in carbon fiber actually does increase its compressive capacity. I ran a check using Sika's software, and adding a wrap increased the compressive capacity of a 12"x12" column by about 40,000 lb.

The reasoning, I believe, is that the carbon fiber prevents the outer edges of the column from blowing out.

Here's a link to their software.

https://usa.sika.com/en/constructio...ce-center/Sika-CarboDur-FRP-design-software.h

 

[jayrod12]

50mm of embedment won't even hold the jacket to the main concrete. Or at least not confidently. Provide real embedment.