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Old Metal Building - Tapered Moment Fra

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Alden,

If you could determine the manufacturer of the metal building, it would 
help.  Frequently they will identify the manufacturer by a name or design at 
peak on the gable end.  The next thing, if you do find out who manufactured 
the building, is trying to find them and getting information out to them.  
There have been a lot of acquisitions in the metal building industry in the 
last 20 years.

One manufacturer that I tried to get information from needed *their* job 
number in order to locate information and that their records were stored in a 
salt mine in New York State (???).  Of course, their job number was nowhere 
on the building.

20 years ago, the metal building manufacturers used nothing less than A36 
steel for their frames.  A36 steel became the de facto structural steel in 
the middle 60s.  Also, about 20 years ago, the metal building industry, IIRC, 
began using plastic design for their buildings.

The design of metal buildings is closer to a gnat's eyebrow than to its anal 
cavity.

It may be possible that the roof beams were tapered beams (deeper at 
mid-span then at ends) manufactured by Riverside Steel.  They tried to 
promote these about 30 or so years ago.

Hope this helps.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Alden Manipula wrote:

. > 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.
. > www.novagroupinc.net