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RE: Old Metal Building - Tapered Moment Frame

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Can you determine who manufactured the building? Usually there's a nameplate. You can probably get the contract number or some other identifying information from such a nameplate if you can find it, and contact the manufacturer.
But if you can't find such information, you can at least ask the manufacturer for their best guess as to the strength of the material used.
You're right about the fact that these buildings were hardly ever built with any fat on them. You will undoubtedly need to design repair material for the girders.

William L. Polhemus, Jr., P.E.
Polhemus Engineering Company
Katy, Texas
Phone 281-492-2251
Fax 281-492-8203

-----Original Message-----
From: Alden Manipula [mailto:amanipula(--nospam--at)]
Sent: Wednesday, March 28, 2001 9:53 AM
To: SEAINT Listserve
Subject: Old Metal Building - Tapered Moment Frame

Hello everyone, 
I'm looking at an old metal building (~20 years old, this is a guess) to which new rooftop units need to be placed upon.  The building system consists of tapared beams ranging from 24" deep to 31" deep w/ 6" wide flanges (tf = .3" and tw=.25").  4 bolt stiffened moment connections at midspan (max span = 46'-0") and over the columns and full welds connecting the tapered sections at about 8'-10' from the columns.  Z-sections at 4' o.c.
Can I analyze the beam lines as a continous beam w/ supports at the column?  Which would mean the largest moments should be at midspan and at the columns.  This makes sense to me and confirms the 4 bolt stiffened connections at those locations. 
My main question is did they use 33/46/50 ksi steel for these things?  I tried looking for a shop stamp on the beams, no luck.
These metal buildings sure are designed to the gnat's ass, aren't they?  I'm guessing that these beams will have to be reinforced w/ plates.
Alden Manipula
Structural E.I.T.