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Re: Fire rate TS

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There may or may not be a UL listed assembly for concrete-filled tubes
(now called HSS for hollow structural sections), but there was a series
of papers in the ASCE Structures Journal by T.T. Lie on the subject that
should help you with fire resistance for such an assembly.

The essence of the papers, as I remember, was that the concrete filling,
with relatively minor longituinal reinforcing steel inside acts
effectively as a heat sink. Also in the papers is how to calculate a
fire rating as a function of the HSS cross sectional dimensions and
concrete heat sink area (somewhat related to each other). The
longitudinal reinforcement, although nominal, was required to maintain
the heat sink because unreinforced concrete filling tended to crack up
into chunks as the moisture in the concrete boiled away and tried to
escape through the ends of the confining HSS. The cracked concrete
filling did not function very effectively as a heat sink.

Although the assembly is probably not cheap to build and install, it
seems like a very viable alternative to sprayed-on fireproofing or
gypsum-board enclosure...particularly if you are looking for a very
clean exposed steel structure.

One other possibility: The United terminal in Chicago's O'Hare Airport
is all exposed steel without fire protection, except in the basement. To
maintain the exposed steel look, they used two nested HSS with a ring of
concrete between them to obtain the necessary fire rating.


Mike Brown wrote:
> I have a quick question that I am hoping somebody can help me with:  Is
> there a fire rating for concrete filled tube steel?  If so, where can I
> get this information?  The UL listing only has assemblies for concrete
> filled pipes.
> Thanks in advanced.
> Michael K. Brown, P.E.
> CSHQA Engineers
> Boise, ID
> mike.brown(--nospam--at)