How do you reinforce a 100 year old cast iron column?

[dlclarkii]

I have a 100 year old building with these beautiful 12" diameter cast iron columns with a 1" wall thickness. A test lab cut a coupon and they did a tensile test on these columns and they're no good. Brittle Failure – no necking, no elongation. So has anyone every dealt with these type of columns in older building and how did you deal with them? How do you reinforce these columns w/o replacing them? Thank you.

 

[MiketheEngineer]

Could you fill them with concrete and rebar??

 

[AlmostPE]

shore the beam, remove the cast iron column, slide a tube steel that would fit in it and weld it together or something. Reinstall the column after the reinforcing the column. Or do what mike suggested.

 

[jike]

I have reinforced these columns by U bolting a channel to it to carry additional minor loads (independent of the column). The column would provide stability to the channel. Since you haven't really explained your problem, I do not know if this may fit your situation or not.

 

[AlmostPE]

It sounds like he does not want to change the appearance of the column.

 

[csd72]

Could you replace it with a replica steel column, painted to resemble cast iron?

They can do this for beds, why not structural steel?

 

[dlclarkii]

Thanks for the replies!

Filling these columns will concrete would significantly increase the load on the existing footings.

I've thought about using a channel on each corner and bolting everything together, that's really the only idea I have.

I've posted a pic in my first post. There's probably 24 of these columns and they're 3 stories tall, supporting a 2nd floor and a roof.

 

[BSE05]

What is generating the concern for these columns?

Are you involved in adding more load or being required to confirm seismic capacity?

There are many buildings of that era with cast iron columns still in service.

 

[dlclarkii]

The concern is they came back no good. We also have to attach shear tabs to these cast iron column to attach WF's in areas where we need to infill the missing 2nd floor.

Here's what the test report shows:

As per your request to set new expansion bolts to frame new steel beams into the existing columns, the following is noted:

1. The material is brittle.
2. The weldability is poor, would require extensive preheating., slow cooling, qualification of procedures, personnel, etc.
3. The strength and toughness are inferior to those of structural steels.

 

[civilperson]

They came back as cast iron, good as the day they were first put in service! To attach shear tabs for WF beams:
1)pre-qualify the weld process and the welders using preheat and suitable materials for both materials.
2)addition of interior HSS to strength existing section may be necessary depending on the added loads proposed.

 

[kelowna]

If the concern is brittleness and not load bearing capacity: Have you considered carbon fiber reinforcement? I have used it once before on a reinforced concrete column with inaddequate steel reinforcement.
It came as a cloth like material which was applied with resin to the surface of the column.
In your case, with round columns, it could be applied easily. It would not improve the compressive strength but you would provide extra bending capacity and confinement.


Another idea would be to provide half circular pipes, with an inner diameter slightly larger than the original column OD and cut outs for the beams. Once installed, weld the two vertical seam welds and install brackets to support the beams around and any new beams. The apparience would not change a lot and you would not need to provide falsework as if you were replacing them.

 

[BSE05]

This report is a brief description of the properties of cast iron. It was commonly used for columns around the turn of the century well into the 1920's. I have a 1931 Kidder handbook with strength tables for cast iron columns.

Boston Building Code 1926 =>Max fiber stress 9000 psi-60L/r with a limiting L/r of 70.

Attachments are another problem. You cannot weld to cast iron. Your picture shows bearing seat through bolted to the cast iron, which was commonly done. However, I would not recommend doing that today. Boxing the cast iron in full height plates or channels for connection points and load transfer to foundations maybe worth pursuing.

But, adding stories, load, etc triggers conforming to lateral seismic requirements which is another series of problems to solve.

 

[samdamon]

DL- Are you adding back dead and live load from a floor that was there at some time in the past but then removed? Perhaps a design check may prove that the column will work as is. If the floor wasn't there before, even then you may be able to take advantage of a reduced unbraced length in the col due to the addition of the floor level. However of course the footing capacity may still be an issue. "Structural Analysis of Historic Buildings" by J Stanley Rabun has a lot useful data on cast iron columns.