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RE: Fire Rating

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Thanks for the info.  By the way, what are you doing working on a Saturday?

Brian

-----Original Message-----
From: Carter, Charlie [mailto:carter(--nospam--at)aisc.org]
Sent: Saturday, February 23, 2002 9:38 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Fire Rating


> I have a partial garage (one row of parking)
> under the main floor of an office.  When we
> began the project, there was no need to fire
> rate the floor between the two.  Now that it
> is permit time, we have to rate the floor system
> separating the two.  My client has faxed over
> some cut sheets from the U.L. manual (I do not
> have copies of the entire manuals).  The particular
> system he chose requires a minimum floor beam
> size of W8x28.  My beams are deeper, but not
> as heavy (short span).  What is U.L.'s criteria
> for MINIMUM?  Is it depth, weight, flange size?

The following answer is from Farid Alfawakhiri, my fire expert colleague
here at AISC:

Charlie

P.S. Note that the information Farid referenced in the AISC Manual gives you
UL assembly numbers. You can go to http://www.ul.com with those numbers and
get all information that is in the U.L. Fire Resistance Directory for that
assembly.

**********************
Any beam of similar shape configuration would usually be acceptable provided
it has a W/D Ratio greater than that for W8x28.

W = weigh of steel member in pounds per foot length
D = perimeter of fire protection for the considered section in inches
(depends whether box or contour fire protection, also depends whether 3 or 4
sides are fire protected)

If there is concrete slab on top of the beam - 3 sides will need fire
protection. For the usual spray applied fire proofing along the contour on 3
sides, W8x28 has D = 34.2" and W/D = 0.819

For a complete explanation see pp. 2-39 through 2-48 of the 3rd Edition of
the AISC LRFD Manual of Steel Construction. Tables  1-36 through 1-53 list
W/D ratios for all common steel sections.

Regards
Farid

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