PEM - Fire Damage

[bookowski]

See attached photo. The beam, in particular the bottom flange, is twisted noticeably to the right.

Overall there was no heat damage or buckling observed in this building. End walls blew out including the columns, but all frames in this area were ok. A lot of collateral damage and soot but members are straight. Is it possible that this visible twist was present before the fire?

Easiest fix to just replace? Heat straightening?

 

[bookowski]

lost the 'B' in my title - pemb

 

[OHIOMatt]

We just engaged in a similar situation, we decided to recommend replacement. PEMB are designed to the limit, so you just don't have any capacity in reserve.

 

[Ron]

bookowski....check the materials for change. Check the steel structural components to see if they have been grossly affected by the fire. This can be done by checking hardness values and comparing with expected values for the materials. In checking the hardness, be sure to sand/grind the first 1/32 to 1/16 of an inch of the surface to get past carburizing effects.

If a section has plastically deformed from the fire...replace it.

 

[bookowski]

OhioMatt - I was leaning that way, replacement. I am just suspicious that this was not caused by the fire. The adjacent flange bracing and roof bracing, both of which are much smaller than the frame, do not show distortion. In general there is no evidence that members experienced a thermal load sufficient to induce any changes. Inspecting the building I found plenty of issues unrelated to the fire (anchor nuts missing or not tightened, a few baseplates that are partially hanging over the footing etc.) and I am thinking that this may be an original defect. I was wondering if anyone had seem similar defects as part of the tolerances in pemb? If it was original does it matter - it seems to be the bottom flange that is out, will the tension in the flange self-stabilize it? Is the bracing enough? I guess there is no way to know so better to replace than theorize why. I just hate to spec such a large replacement if unnecessary.

I don't have much faith in testing the hardness values. I believe that there is probably enough variation in values that without having a pre-fire calibration it wouldn't be informative. Regardless I don't see any indication that temperatures or duration were near the point to cause plastic deformation.

 

[bookowski]

One more pic

 

[SteelPE]

What is the difference if the flange was damaged before or after the fire? I highly doubt that frame was designed with a bent flange. In this instance, the owner may "luck out" and get the insurance to cover the repair.

 

[dik]

It appears that the member has deformed from the fire and I would consider replacing it. Ron notes that you can obtain tests by grinding off 1/32 or so of material... but, in doing so you likely have reduced the capacity by half (<G>).

If the original supplier is around, you may want an opinion from their engineer and what is required to warranty the building... building could be old enough or supplier is 'gone'... that there may be no warranty in the first place.

Dik

 

[Splitrings]

What type of metal siding is that? It just doesn't look like that was a very hot fire. None of the members are rusted, if they are steel. If that is aluminum siding and its still there, its an indication the temps were pretty low. It looks like a fire that lacked sufficient oxygen and it generated significant soot.

 

[RFreund]

Attached is a decent article on fire damage with some suggestions for determining temperature.


EIT

http://www.HowToEngineer.com

 

[RFreund]

take 2

EIT
www.HowToEngineer.com

 

[bookowski]

I recommended that it be replaced. The building is almost brand new - about a year old I believe. I agree that it does not appear that the fire was very hot, and it was extinguished in a matter of minutes (they estimated less than 4) which is why I was wondering if that was possibly an original defect and if anyone has seen anything like that in a pemb. Thanks for the input.