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RE: Assessing fire damage to steel

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>Does anyone have recommendations for
>determining the in-place acceptability 
>of steel which has been subject to a
>fire in a metal building?

One good paper on this topic is in the AISC Engineering Journal:

    Tide, R.H.R., 1998 (First Quarter), "Integrity of
    Structural Steel After Exposure to Fire"

You can access this paper for free if you are an AISC member here:
www.aisc.org/epubs.

An older similar reference is 

    Dill, F. H., "Structural Steel After a Fire,"
    Proceedings of National Steel Construction Conference,
    May 5-6, Denver, CO, American Institute of Steel
    Construction, Chicago, IL, 1960.

You can get this paper by contacting the AISC Steel Solutions Center:
solutions(--nospam--at)aisc.org or 866.ask.aisc.

And there are many other references from those references, as well as
information here:

    www.aisc.org/fire
    www.aisc.org/facts


>I expect to (eventually) remove coupons from the
>primary members for testing, just as I would for
>any material of questionable heritage, for strength
>and ductility.

As you will read in these references, this is rarely necessary.
Essentially, you can look at main members visually. If there is no
deformation, there was no significant heating. If there is deformation,
it is a question of whether the deformation needs to be (or can be)
straightened out. If the deformation exceeds whatever limits are
established as acceptable, it is then a question of whether it is more
economical to straighten it in place or cut it out and replace it.

One of the advantages of steel in fire applications is that it regains
its pre-fire properties after the fire. The exception to this is when
the fire is so intense and local to the steel that there is pitting of
the steel. This is easily determined visually as well.


>However, the issue of bolt strength (especially
>@ foundation) and near-foundation interface steel
>is a bit more troublesome, as getting samples
>which will not affect the structure (or can be
>removed & replaced) may prove impractical.

High-strength bolts can be affected in a fire. I'd concentrate the
evaluation on areas that have main members with damage of significance.
Heat can affect bolt strength, since HS bolts are quenched and tempered
products. But it would have to get hot enough to have damage in the main
members. Pull a few bolts and test them for strength to see what
happened.

In looking at foundation fasteners, I'd first decide if they would even
need to be there in a completed structure before trying to determine if
they are damaged.


>I'm considering looking for a lab which can do
>on-site eddy-current NDE, but I've not used
>this method and don't know quite how interpretable
>the results are.

This would probably just spend money without much benefit. See the
recommendations in those papers above.


>I'm fairly certain that there will be areas of
>the building which were unaffected but built
>identically, so I will likely have a "control"
>sample for any destructive or NDE tests.

I'd only see this as a necessity if you find significant anomalies in
the damaged stuff you look at. You should be able to tell what's good
and what needs to be replaced without hacking into the rest of the
structure.


Hope this helps. Let me know if you need further information.

Charlie







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