Large structural frame that has permanet deflections. How to repair?

[EngineerDavid]

I am looking at a large steel frame with an internal plated chamber supported by the steel framework. The rectangular chamber is about 100ft by 20 ft by 75 ft high. There was an overpressure that has caused the plates and the structure to permanently deform. The customer wants to fix rather than replace the columns since there is so much connected to them. If we pull/push on the columns to correct the deflection, which is on the order of 4 to 5 inches over the 75 foot height, do you reinforce the columns to account for the loading needed to have caused the deflection? The columns are 18 inch diameter HSS shapes and W12 X 65's so the loading needed to correct these members is significant. Thank you

 

[flight7]

What do you mean by overpressure? Explosion?

 

[EngineerDavid]

No, it was a pressure testing situation for a new chamber and the pressure that developed inside exceeded the design values due to an error by an operator. The chamber platework bulged and then welds broke which relieved the overpressure but not before there was permanent deformation. I assume that the design loads were also not correct since there could develop these larger values.

 

[JStephen]

Don't know if it's an option for you, but google up "flame straightening".

I would also look very carefully at the option of using any/all members without staightening them.

 

[msquared48]

Is this a controlled volume testing chamber where you MUST have that particular volume?

Mike McCann
MMC Engineering

 

[EngineerDavid]

There is not a specific volume required. It just must be large enough to enclose the equipment required to be inside.

 

[SAIL3]

Push/pull correction, as you said, may require significant loads and trying to controll where the resulting deflection ends up is not guaranteed...may also cause other unintended damage.
One also has to have something to push or pull against.
If the operating performance of the system is not affected by this deflection you have now, maybe installing sister columns at each deflected col and connected to it so that it picks up the load in the damaged col might be the more economical fix.
May have to do some creative design at the fdn, though.
All other members/connections should be checked also for damage.

 

[paddingtongreen]

I would start with what I have, it makes more sense. Can I add material to make it usable, rather than the iffy process of straightening. If straightening is required, I would only consider heat straightening, Push/pull would be tricky, as SAIL3 points out, and I would worry about the already warped/damaged joints.

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

 

[EngineerDavid]

Thank you. The straightening is required by the final customer and will be needed for the operation of the chamber. I agree that the heat straightening is the only way to proceed but it will be a difficult process since the structure is so large. My next step is to check with contractors who have experience with heat straightening or thermal upsetting and see if it is possible. Then there are the connections to investigate. Surprisingly there were no cracked welds visible in the member end connections, which were essentially end plates welded to the beams and bolted to the columns. Need to do some testing of the welds to verify their integrity. Great feedback.

 

[csd72]

There may be additional pressure vessel issues such as fatigue that need to be looked at.

 

[MikeHalloran]

Operator errors tend to recur.
This would be a good time to install pressure and vacuum relief valves, with appropriate fixed settings.
I would go so far as to conceal or disguise them to reduce the probability of removal.







Mike Halloran
Pembroke Pines, FL, USA