Existing Pipe Column Strengthening

[Stenbrook]

I have an existing 6" Std Pipe column that needs to be strengthened. I am semi familiar with the strengthening of a wide flange column but am not sure about a pipe column and if the design method or detailing is different.

Any help or advice would be much appreciated.

 

[KootK]

Same methods, trickier details maybe. You could attach a pair of channels to the pipe with slot welds through the webs perhaps? Large diameter flare bevel welds always make me nervous. I've had quality control issues with them in the past.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Stenbrook]

It looks like the channels to column with the flanges of the channel being welded to the column will be the way I will detail it. (I was already looking at using this detail before you said a pair of channels so it must be a good idea)

 

[KootK]

A custom WT shape on each side with the stems welded to the tube would be effective and pretty weld friendly.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Lomarandil]

Is it possible to infill the pipe column and add strength that way?

 

[Stenbrook]

I considered filling in with concrete or grout, but I believe that may be more complicated then just welding a steel section to the column. I could be wrong though

 

[jayrod12]

I believe there have also been many studies done that prove filling with grout doesn't really increase the capacity a considerable amount. It would be effective in stopping the wall from buckling locally however the overall capacity doesn't increase due to strain incompatibility (if I remember correctly)

 

[KootK]

The AISC manual has tables for concrete filled HSS. You get something but, for this size of column, it isn't much. I know because I've tried it before in desperation.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[msquared48]

You get up to a 30% increase in capacity per the tables.

Mike McCann, PE, SE (WA)

 

[oldestguy]

High strength low shrinkage grout done from bottom up would be simple for a grout contractor, probably less than an hour's time. As to buckling, what does the pipe do? It has to change the configuration of the cross section some. A hardened grout has no place to go, restricting that change. You wouldn't be looking at the compressive strength increase as critical.

A simple test would be to fill a Shelby tube with grout and run a column type compression test in the concrete test lab and it will demonstrate what goes on.

 

[msquared48]

I have used this method to strengthen the pipe column legs of telecom towers several times. You pump the non-shrink grout in from the bottom using a special connection and stop when it shows at
a new inspection port a the top. No worries.

Mike McCann, PE, SE (WA)

 

[dhengr]

Stenbrook:
Depending upon the exact weakness of your 6" Std. pipe col., you might consider 4-2x2 angles, toes in, welded to the pipe. No greater in square size than the col. dia. and they can be oriented to fit within a wall or oriented to best strength advantage. Non-shrink grouting from the bottom up also adds compressive strength and improves buckling conditions.

 

[RareBugTX]

Could you attach an 8" pipe cut in half (lenghtwise) and then welded to the existing 6"?