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Bar Joists

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According to the SJI 50-year digest that I have, an 18H5 joist spanning 30 
feet has an allowable total load of 241 #/ft; with a maximum live load (the 
live load that will produce a deflection of L/360) of 157 #/ft.  (Maximum 
moment capacity: 325,000 in-lbs; maximum reaction: 4500 lbs; approximate 
weight: 8 lbs/ft)

Based purely on my observations, the letter designations refer to:

J     Joists (22 ksi allowable stress)
H     High Strength Steel (30 ksi vs. 22 ksi for J-joists)
L     Long Span
D     Deep

The Steel Joist Institute puts out a compilation of specifications and load 
tables ranging from 1928 to somewhere near current.  (I have the 50-year 
edition from 1928-1978 and I believe that there is a more current edition 
available.)  For anyone dealing with old buildings, this, together with 
AISC's "Iron and Steel Beams" book, is a "must have."

Hope this helps.

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

Todd Hill wrote:

>>I have structural drawings dated 1978 for a project in Oklahoma.
The drawings call out a 18H5 joist on 5'-0" centers, spanning 30'-0".
Anyone know what the capacity for this joist would be?
Anyone know what the history of this lettering for steel joists?
Most recent catalogs I have, list K series joists.
I also have older information on J series joists.
What do the letters actually mean?

Todd Hill
TK Architects, Inc.
816-842-7552 ext. 233<<

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