Steel bar joists: What do the designations mean?

[Jerry Peck - Codeman]

(From a phone call question.)

Codeman,

I'm looking at some plans and the steel bar joists have numbers indicating which joist is where. What designation code is used and what do the numbers and letter mean?

Thanks,

Dan

[Jerry Peck - Codeman]

Dan,

Steel bar joists are manufactured in several different “series”, with each series being designed for specific span and load purposes.

Bar joists are designated by a three-part code on plans. The first part of the code is a number, the second part is a letter or series of letters, the third part is a number. The first part of the code tells you that the joist's depth. The second part of the code indicates the "series" the joist is, with the third part of the code indicating the make-up of the chord cross-section.

Below as the letters used to indicate the "series" of the steel bar joist, with minimum and maximum joist depths for a given "series" along with the various chord sections for each "series".

K series - Common open web joists - These common open web joists are standard sized joists used for typical applications. The span of K series joists is from 8 feet to 60 feet, and have depths of 8 inches to 30 inches. The K series joists have chord section numbers from 1 to 12. The smallest K series joist is an 8K1 and spans up to 16 feet. The largest K series joist is a 30K12 and spans from 30 feet to 60 feet.

CS series - Constant Shear - These CS joists are specially designed for non uniform loads and concentrated loads. The CS series joists have joist depths of from 10 inches to 30 inches with chord section numbers from 1 to 5.

LH series - Longspan - These LH joists span from 25 feet to 96 feet (over 50% greater span than the K series joists, limited to 60 feet). The LH joist depths are from 18 inches to 48 inches with chord section numbers from 2 to 17.

DLH series - Deep Longspan - These DLH joists can span even longer than longspans. The DLH joist can span from 89 feet to 144 feet and have depths of 52 inches to 72 inches. The DLH chord section numbers run from 10 up to 19.

SLH series - Super Longspan - These SLH joists are even deeper than DLHs and can span almost twice as long as the DLH joists. These super large SLH joists span from 111 feet to 240 feet with depths from 80 inches (a standard door is 80 inches high) to 120 inches (that's 10 feet, or 2 feet higher than the standard 8 foot residential ceiling). The chords section numbers are from 15 to 25.

Following is a listing of the Weight per Linear foot of Bar Joists, the attachment is from here (NOTE: Place mouse over link, right click to show menu, select 'Open Link In New Window' or similar option.): http://www.mc2-ice.com/support/estref/p ... joists.htm

Codeman