Removing Temporary Steel Column 2

[asixth]

Hi

I have a temporary steel column (310UC158) that will need to be removed in the future. The column we be approximately 2,000kN (450kips) in compression and I am expecting the structure above to deform approximatley 2.0mm (1") when the column is removed. How would the column safely be removed? I was hoping to heat the steel so that it would soften and deform whilst still loaded and can be sefely removed. Has any done anything similar to this or have any recommendations?

 

[ztengguy]

I would shore on each side with jacks and take the load, remove the column, let the load off the jacks. That much load, I would get some professionals that do it all the time.

 

[kylesito]

Agree with ztengguy...that's the right approach. Take the load off and then use something that you have control over to release the load slowly back into the system. My concern with heating it is that it's a very uncontrolled method and there is no redundancy if you need to stop the process mid way through. With the screw or hydraulic jacks doing the work for you, you always have the option of pausing or slowing the process if you need to address safety or logistical concerns.

PE, SE
Eastern United States

"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
~Code of Hammurabi

 

[swearingen]

I've done this several times in my career and we always did as ztengguy and kylesito say. I agree with them.


-5^2 = -25 ;-)

http://www.eng-tips.com/supportus.cfm

 

[PEinc]

It seems to me that not enough information has been provided to give an answer. For instance, wouldn't the removal procedure depend on whether or not a new permanent column has been installed before removing the temporary column? Obviously, some type of work or modification has been performed if a temporary column can now be removed.

http://www.PeirceEngineering.com

 

[ztengguy]

@ PEinc, I guess we just assumed that. He asked for a process of removing the column, not whether its ok to remove the column.

 

[racookpe1978]

Better look agina at your calculations and units.

you claim it will move 2 mm - then convert that to 1 inch (25 mm). Do you mean 1/10 of one inch?

Yes, you've probably just skipped a decimal, but 1 inch (25 mm) of "sag" is NOT trivial!

 

[ztengguy]

What if its a 80' span? is 1" too much now?

 

[msquared48]

You guys are over-thinking the problem here. Just have some fun and blow it in place.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[TLHS]

If the column's really tall, or otherwise difficult to shore up, you could probably install some brackets near the base of the column that will let you jack it directly, lift the load off the base plate, shorten the column by cutting the column below the brackets or removing grout, and then lower the whole thing.

 

[asixth]

Yeah sorry, 1/10". My conversions are terrible.

Thanks for the replies everyone.

 

[MiketheEngineer]

Get a lumber jack to beat it out with a sledge

 

[MrHershey]

Jack it up, cut the column out, let it back down.

 

[ztengguy]

Just something to think about, is the column on a higher up floor? Check your floor for the shoring load you will put into it, would hate to have your jacks punch through the floors.

 

[Archie264]

Not to chase this rabbit trail too far but a temporary column supporting a 450 kip load that will only cause 1/10" of an inch of deflection when removed? That's either a very stiff beam or a very short span...

 

[PEinc]

We just finished temporarily supporting 4 columns (3 concrete columns and 1 big old riveted steel column) in the basement of the Philadelphia Museum of Art. The column loads ranged from 75 to 425 kips. We installed micropiles, with cap beams and jacking beams, as the temporary columns and then jacked the existing columns and/or attached floor beams until they just started to rise. Then we removed the concrete columns and shortened the bottom of the steel column. Later, after the new columns were installed and their loads were transferred, the temporary micropile columns and beams were just burned out. There were no significant structure movements.

http://www.PeirceEngineering.com

 

[Archie264]

PEinc, you're describing replacing old columns with new columns. Unless I misread it it seems original poster is referring to the complete removal of a column.

 

[paddingtongreen]

Use a sand jack. Essentially a box of sand with a plunger sitting on the sand. The box has a hole in the side with a nut or threaded plate welded over it with a bolt inserted. build on the plunger and when done, pull the bolt and either rod or blow the sand out through the bolt hole, allowing the plunger to fall into the box.

We made these with pipes of different size with a plates welded T&B to the smaller plunger. Enclosed compacted sand will take a high compression.

In some cases, these were preloaded with welded metal tabs to hold the pre-compression. These had to be knocked off before removing the sand.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[PEinc]

Archie264, the original poster doesn't give enough info to know what is being done. And, that was my original point. That being said, how you remove a temporary column depends on several things that were never mentioned. But that doesn't seem to stop people from having an exact answer. My second posting shows that it can be possible to just burn out a temporary column under the right circumstances.

http://www.PeirceEngineering.com

 

[Archie264]

PEinc,

I agree that it's possible to remove columns and that it's done all the time, in the right circumstances, of course. Rightly or wrongly I was just fixating on the 450 kips with 1/10" deflection...something there seems off if the column is actually permanently removed.

By the way, as a point of interest, a former boss of mine was involved with the removal of a column in a historical structure of some sort. He had performed all the calculations demonstrating that it was viable and on the day of removal he had installed a strain gauge on the beam to monitor the results. When the column was removed the strain gauge read...nothing. So he started looking at the equipment trying to figure out what was wrong with the installation of the gauge and after about a minute or so the strain gauge slowly started to register the load. What he saw was the evidence of the plastic creep as the molecules rearranged themselves as they let each other know that there was a new load in town.